how to set CFLAGS variable for compiling Xorg

[ludo]

Hi,

I'd like to compile Xorg with debugging info (-g3 -O0 flags)
I have tried to use
    make CFLAGS=<my flags>
but this method corrupts the entire command line

for exemple in libXfont

With the standard 'make', it works well
$ make
[...]
make[3]: Entering directory 
`/d/sources/xorg-git-auto/libXfont.dummy/src/fontfile'
[...]
  gcc -DHAVE_CONFIG_H -I. -I../.. -I../../include/X11/fonts 
-I../../include 
-DFONT_ENCODINGS_DIRECTORY=\"/d/sources/xorg-git-auto/root/lib/X11/fonts/encodings/encodings.dir\" 
-Wall -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes 
-Wmissing-declarations -Wnested-externs -fno-strict-aliasing -g -O2 
-D_BSD_SOURCE -DHAS_FCHOWN -DHAS_STICKY_DIR_BIT 
-I/d/sources/xorg-git-auto/root/include -MT bitsource.lo -MD -MP -MF 
.deps/bitsource.Tpo -c bitsource.c  -DDLL_EXPORT -DPIC -o .libs/bitsource.o

But If I try to set CFLAGS, make failed
$ make CFLAGS="-g3 -O0"
[...]
make[3]: Entering directory 
`/d/sources/xorg-git-auto/libXfont.dummy/src/fontfile'
[...]
  gcc -DHAVE_CONFIG_H -I. -I../.. -I../../include/X11/fonts 
-I../../include 
-DFONT_ENCODINGS_DIRECTORY=\"/d/sources/xorg-git-auto/root/lib/X11/fonts/encodings/encodings.dir\" 
-g3 -O0 -MT bitsource.lo -MD -MP -MF .deps/bitsource.Tpo -c bitsource.c  
-DDLL_EXPORT -DPIC -o .libs/bitsource.o
In file included from bitsource.c:37:
../../include/X11/fonts/fntfilst.h:38:21: X11/Xos.h: No such file or 
directory


When I set CFLAGS, the command line is modified :
"-g -O2" is replaced by "-g3 -O0" (that's perfect)
but
"-Wall -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes 
-Wmissing-declarations -Wnested-externs -fno-strict-aliasing" is removed
"-D_BSD_SOURCE -DHAS_FCHOWN -DHAS_STICKY_DIR_BIT 
-I/d/sources/xorg-git-auto/root/include" is also removed

What is the correct way for passing additionnal parameters to gcc from 
make ?

thanks