I get this error when using the gst-build:

ninja: Entering directory `build/'
[10/1740] 'Generating GstValidate-1.0.gir with a custom command.'
FAILED: subprojects/gst-devtools/validate/gst/validate/GstValidate-1.0.gir 
'g-ir-scanner' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-runner.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-reporter.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-monitor.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-element-monitor.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-bin-monitor.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-pipeline-monitor.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-pad-monitor.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-monitor-factory.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-report.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-override.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-utils.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-override-registry.c' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor.c' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor-writer.c' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor-parser.c' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-media-info.c' '../subprojects/gst-devtools/validate/gst/validate/validate.c' '../subprojects/gst-devtools/validate/gst/validate/validate.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-types.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-bin-monitor.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-pipeline-monitor.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-element-monitor.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-enums.h' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor.h' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor-writer.h' '../subprojects/gst-devtools/validate/gst/validate/media-descriptor-parser.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-monitor-factory.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-monitor.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-override.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-override-registry.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-pad-monitor.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-reporter.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-report.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-runner.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-scenario.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-utils.h' '../subprojects/gst-devtools/validate/gst/validate/gst-validate-media-info.h' '-pthread' '-I/usr/include/gobject-introspection-1.0' '-I/usr/include/glib-2.0' '-I/usr/lib/x86_64-linux-gnu/glib-2.0/include' '--no-libtool' '--namespace=GstValidate' '--nsversion=1.0' '--warn-all' '--output' 'subprojects/gst-devtools/validate/gst/validate/GstValidate-1.0.gir' '-I/home/phil/gst-build/subprojects/gst-devtools/validate/gst/validate' '-I/home/phil/gst-build/build/subprojects/gst-devtools/validate/.' '-I/home/phil/gst-build/subprojects/gst-devtools/validate/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '--include=GObject-2.0' '--include=GLib-2.0' '--include=Gio-2.0' '--include=GModule-2.0' '--include=GstVideo-1.0' '--include=Gst-1.0' '--include=GstPbutils-1.0' '--symbol-prefix=gst_' '--identifier-prefix=Gst' '--pkg-export=gst-validate-1.0' 'parse' '-I/home/phil/gst-build/build/subprojects/gstreamer/.' '-I/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/usr/include/glib-2.0' '-I/home/phil/gst-build/subprojects/gstreamer/libs' '-I/usr/include/orc-0.4' '/home/phil/gst-build/build/subprojects/gstreamer/gst/..' '-I/home/phil/gst-build/subprojects/gstreamer/.' '.' '-pthread' '-I/usr/include/json-glib-1.0' 'gst-libs' '-I/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs' '-I/usr/lib/x86_64-linux-gnu/glib-2.0/include' 'libs' '-I/home/phil/gst-build/build/subprojects/gstreamer/libs' '-I/home/phil/gst-build/subprojects/gst-plugins-base/gst-libs' '-lgobject-2.0' '-L/home/phil/gst-build/build/subprojects/gstreamer/gst' '-lgstreamer-1.0' '-L/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs/gst/video' '-lgstbase-1.0' '-lgstvideo-1.0' '-L/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs/gst/pbutils' '-lgio-2.0' '-lgsttag-1.0' '-lm' '-pthread' '-L/home/phil/gst-build/build/subprojects/gstreamer/libs/gst/base' '-lgmodule-2.0' '-lgstpbutils-1.0' '-ljson-glib-1.0' '-lgstaudio-1.0' '-lglib-2.0' '-L/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs/gst/tag' '-L/home/phil/gst-build/build/subprojects/gst-plugins-base/gst-libs/gst/audio' '-lorc-0.4' '--add-include-path=/home/phil/gst-build/build/subprojects/gstreamer/gst' '-L/home/phil/gst-build/build/subprojects/gst-devtools/validate/gst/validate' '--library' 'gstvalidateplugin'
Couldn't find include 'GstVideo-1.0.gir' (search path: '['/home/phil/gst-build/build/subprojects/gstreamer/gst', '/usr/share/gnome/gir-1.0', '/home/phil/.local/share/flatpak/exports/share/gir-1.0', '/var/lib/flatpak/exports/share/gir-1.0', '/usr/local/share/gir-1.0', '/usr/share/gir-1.0', '/usr/share/gir-1.0', '/usr/share/gir-1.0', '/usr/share/gir-1.0']')
[35/1740] Compiling c object 'subprojects/gst-plugins-good/tests/check/elements/rtpjitterbuffer@exe/elements_rtpjitterbuffer.c.o'
ninja: build stopped: subcommand failed.

$ find -name "*.gir"
./build/subprojects/gstreamer/gst/Gst-1.0.gir
./build/subprojects/gstreamer/libs/gst/base/GstBase-1.0.gir
./build/subprojects/gstreamer/libs/gst/net/GstNet-1.0.gir

gst-plugins-base hasn't been built yet it seems. Looking at subprojects/gst-devtools/validate/gst/validate/meson.build I see no explicit dep on -base.