+printf "Checking for GL window-system-binding headers:\n"
+have_gl_winsys=0
+
+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 ${gl_cflags} > /dev/null 2>&1
+then
+ printf "Yes.\n"
+ have_gl_winsys=1
+ have_glx=Yes
+else
+ printf "No.\n"
+fi
+rm -f glx-minimal glx-minimal.c
+
+printf " Checking for GL/egl.h... "
+have_egl=No
+if pkg-config --exists egl; then
+ printf "Yes.\n"
+ have_egl=Yes
+ egl_cflags=$(pkg-config --cflags egl)
+else
+ printf "#include <GL/egl.h>\nint main(void){return 0;}\n" > egl-minimal.c
+ if ${CC} -o egl-minimal egl-minimal.c ${gl_cflags} > /dev/null 2>&1
+ then
+ printf "Yes.\n"
+ have_gl_winsys=1
+ have_egl=1
+ else
+ printf "No.\n"
+ fi
+ rm -f egl-minimal egl-minimal.c
+fi
+
+if [ $have_gl_winsys -eq 0 ]; then
+ errors=$((errors + 1))