A jhbuild run was stopped by this failure:

make[5]: Entering directory '/home/nili/jhbuild/checkout/gst-plugins-base/gst-libs/gst/rtsp'
  CC       libgstrtsp_1.0_la-gstrtsptransport.lo
  CC       libgstrtsp_1.0_la-gstrtspurl.lo
  CC       libgstrtsp_1.0_la-gstrtspmessage.lo
make[5]: *** No rule to make target 'gstrtsp-marshal.list', needed by 'gstrtsp-marshal.h'.  Stop.
make[5]: *** Waiting for unfinished jobs....
  CC       libgstrtsp_1.0_la-gstrtspdefs.lo
  CC       libgstrtsp_1.0_la-gstrtspconnection.lo
make[5]: Leaving directory '/home/nili/jhbuild/checkout/gst-plugins-base/gst-libs/gst/rtsp'
Makefile:620: recipe for target 'all' failed
make[4]: *** [all] Error 2
make[4]: Leaving directory '/home/nili/jhbuild/checkout/gst-plugins-base/gst-libs/gst/rtsp'
Makefile:575: recipe for target 'all-recursive' failed
make[3]: *** [all-recursive] Error 1
make[3]: Leaving directory '/home/nili/jhbuild/checkout/gst-plugins-base/gst-libs/gst'
Makefile:556: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/home/nili/jhbuild/checkout/gst-plugins-base/gst-libs'
Makefile:687: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/nili/jhbuild/checkout/gst-plugins-base'
Makefile:616: recipe for target 'all' failed
make: *** [all] Error 2
*** Error during phase build of gst-plugins-base: ########## Error running make -j 9  *** [33/89]

I chose "wipe directory and start over", and it worked the second time.