Mine

15:05:36:671:root@fionnay:/tmp# ./problem.sh
#!/bin/sh -xv

LD_LIBRARY_PATH="/usr/X11R6/lib:/usr/include/gtk-2.0/gtk/"
+ LD_LIBRARY_PATH=/usr/X11R6/lib:/usr/include/gtk-2.0/gtk/
echo /usr/include/glib*/*/glib.h
+ echo '/usr/include/glib*/*/glib.h'
/usr/include/glib*/*/glib.h
ldconfig && depmod -a
+ ldconfig
+ depmod -a
cat /tmp/test.c
+ cat /tmp/test.c
#include <glib.h>

int main() { return 0; }
cc /tmp/test.c
+ cc /tmp/test.c
/tmp/test.c:1:18: error: glib.h: No such file or directory