progs/glsl: Ensure CFLAGS are passed during linking

progs/glsl: Ensure CFLAGS are passed during linking

Commit ab6825b3e3fd04564b7840e945fa32b0a7b3c0c2 fixed an issue where the
architecture option -m32 wasn't being passed to the compiler when
linking .o files. This would only fix the issue with user's building
with the hacky --enable-32-bit. The right way to fix this is to pass
CFLAGS to the linker, which the GNU make builtin rules unfortunately
don't do.

Signed-off-by: Dan Nicholson <dbn.lists@gmail.com>
Tested-by: Török Edwin <edwintorok@gmail.com>