I think the mingw32-gettext.xml file lacks a dependency (libexpat)
for the -dev package (installed by mingw32-autotools if I understand
correctly):

<component class="dev">
   <release tarname="gettext-0.18.1.1-2-mingw32-dev.tar.lzma" >
      <requires eq="mingw32-libgcc-*-mingw32-dll-1.tar" />
      <requires eq="mingw32-libgettextpo-%-mingw32-%-dll-0.tar" />
      <requires ge="mingw32-libiconv-1.14-2-mingw32-*-dll-2.tar" />
      <requires eq="mingw32-libintl-%-mingw32-%-dll-8.tar" />
   </release>

Indeed gettext-0.18.1.1-2-mingw32-dev.tar.lzma contains xgettext.exe
that requires libexpat-1.dll

On a typical install, it's not a problem because it's installed along gdb, but
I don't install gdb. I'm compiling something, the configure script detects
xgettext.exe and tries to launch it... That's how I found out the issue.

If I'm wrong, sorry, it's probably I just didn't understand how mingw-get works.

Regards