I'm building gnome-power-manager via JHBuild. gnome-power-manager builds
successfully. If upstream then updates configure.ac, then I run 'make', which
attempts a reconfigure, but fails.

This is because JHBuild sets ACLOCAL_FLAGS to include the sandbox (e.g. -I
/opt/gnome/share/aclocal). One may argue it is silly for JHBuild to require
every module to support ACLOCAL_FLAGS, but there isn't a way around it until
automake-1.12 is out - which includes support for ACLOCAL_PATH. Further details
in the JHBuild bug 634617.

The build failure is:
make  V=1
CDPATH="${ZSH_VERSION+.}:" && cd . && /bin/sh /home/Oxyde/gnome/gnome-power-manager/missing --run aclocal-1.11 -I m4
configure.ac:98: warning: macro `AM_GLIB_GNU_GETTEXT' not found in library
 cd . && /bin/sh /home/Oxyde/gnome/gnome-power-manager/missing --run automake-1.11 --foreign
CDPATH="${ZSH_VERSION+.}:" && cd . && /bin/sh /home/Oxyde/gnome/gnome-power-manager/missing --run autoconf
configure.ac:98: error: possibly undefined macro: AM_GLIB_GNU_GETTEXT
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
make: *** [configure] Error 1