glib preprocessor strangeness

[Thomas Stover <thomas wsinnovations com>]

Ok so in the setup I've got, this works:

$PKG_CONFIG_PATH=/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib/pkgconfig/ 
/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/bin/arm-unknown-linux-gnu-gcc 
`pkg-config --cflags glib-2.0`  glibtest.c `pkg-config --libs glib-2.0`

Which it is suppose to. Yet while trying to debug a scons issue, I find 
my way to this quagmire. Examining the pkg-config output yields:

$ 
PKG_CONFIG_PATH=/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib/pkgconfig/ 
pkg-config --cflags glib-2.0
outputs:
-I/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/include/glib-2.0 
-I/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib/glib-2.0/include  


and $ 
PKG_CONFIG_PATH=/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib/pkgconfig/ 
pkg-config --libs glib-2.0
outputs:
-L/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib 
-lglib-2.0

OK that all makes sense, and is expected. Now here is the punchline - 
this fails:

$/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/bin/arm-unknown-linux-gnu-gcc 
-Wall  
-I/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/include/glib-2.0 
-I/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib/glib-2.0/include 
glibtest.c 
-L/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/lib 
-lglib-2.0

with this error: 
/opt/crosscompilers/gcc-4.0.1-glibc-2.3.5/arm-unknown-linux-gnu/include/glib-2.0/glib/gtypes.h:34:24: 
error: glibconfig.h: No such file or directory

I can't find a glibconfig.h anywhere. Not even in the glib build tree. 
I've tried other programs that repeat this same behavior. I've got 
nothing. Help much appreciated.