Another cosmetic improvement to simply align the output more cleanly.
printf "Checking for GL window-system-binding headers:\n"
have_gl_winsys=0
-printf " Checking for GL/glx.h... "
+printf " Checking for GL/glx.h... "
have_glx=No
printf "#include <GL/glx.h>\nint main(void){return 0;}\n" > glx-minimal.c
if ${CC} -o glx-minimal glx-minimal.c ${gl_cflags} > /dev/null 2>&1
fi
rm -f glx-minimal glx-minimal.c
-printf " Checking for GL/egl.h... "
+printf " Checking for GL/egl.h... "
have_egl=No
if pkg-config --exists egl; then
printf "Yes.\n"