build: remove checks for libGL

We don't need to link against libGL directly, nor do we need OpenGL
headers. The only thing we need is the windowing interop stuff, such as
libEGL.

waftools/checks/custom.py

@@ -144,7 +144,6 @@ def check_rpi(ctx, dependency_identifier):
     checks = [
         check_pkg_config('bcm_host', uselib_store='bcm_host'),
         check_pkg_config('egl'),
-        check_pkg_config('glesv2'),
         check_cc(lib=['mmal_core', 'mmal_util', 'mmal_vc_client'], use=['bcm_host']),
     ]
 

wscript

@@ -610,16 +610,13 @@ video_output_features = [
         'desc': 'OpenGL X11 EGL Backend',
         'deps': [ 'x11' ],
         'groups': [ 'gl' ],
-        'func': check_pkg_config('egl', 'gl'),
+        'func': check_pkg_config('egl'),
     } , {
         'name': '--egl-drm',
         'desc': 'OpenGL DRM EGL Backend',
         'deps': [ 'drm', 'gbm' ],
         'groups': [ 'gl' ],
-        'func': compose_checks(
-            check_pkg_config('egl'),
-            check_pkg_config_cflags('gl')
-        )
+        'func': check_pkg_config('egl'),
     } , {
         'name': '--gl-wayland',
         'desc': 'OpenGL Wayland Backend',
@@ -743,7 +740,6 @@ video_output_features = [
         'deps': ['libdl'],
         'func': compose_checks(
             check_cc(lib="EGL"),
-            check_cc(lib="GLESv2"),
             check_statement('EGL/fbdev_window.h', 'struct fbdev_window test'),
             check_statement('linux/fb.h', 'struct fb_var_screeninfo test'),
         ),