I've been following the git master for a long time.   I tried upgrading today.   The build fails with:

 CC       soup-client-input-stream.lo
In file included from /usr/include/stdio.h:74:0,
                 from /opt/garnome-3.21/include/glib-2.0/glib/gmessages.h:33,
                 from /opt/garnome-3.21/include/glib-2.0/glib.h:62,
                 from /opt/garnome-3.21/include/glib-2.0/gobject/gbinding.h:28,
                 from /opt/garnome-3.21/include/glib-2.0/glib-object.h:23,
                 from /opt/garnome-3.21/include/glib-2.0/gio/gioenums.h:28,
                 from /opt/garnome-3.21/include/glib-2.0/gio/giotypes.h:28,
                 from /opt/garnome-3.21/include/glib-2.0/gio/gio.h:26,
                 from soup-types.h:9,
                 from soup-client-input-stream.h:9,
                 from soup-client-input-stream.c:12:
soup-client-input-stream.c:21:2: error: expected identifier before ‘(’ token
  EOF,
  ^
soup-client-input-stream.c:25:22: error: ‘LAST_SIGNAL’ undeclared here (not in a function)
 static guint signals[LAST_SIGNAL] = { 0 };
                      ^
soup-client-input-stream.c:25:14: warning: ‘signals’ defined but not used [-Wunused-variable]
 static guint signals[LAST_SIGNAL] = { 0 };
 
This happens on an i686 and an x86_64, both running slackware.