Ensure we use the right OpenGL libs.

After c512578 , even though we're no longer compiling OpenGL ES
support when Qt wasn't compiled to use Qt, we were still linking OpenGL
ES libs on systems with OpenGL ES development packages installed.  This
change should ensure we use OpenGL ES libs only when using a Qt version
compiled against OpenGL ES, and use non-ES libs when using a Qt version
compiled against non-ES OpenGL.

This seems like it should work for all systems--Qt using OpenGL with
OpenGL installed on the system (regardless of whether OpenGL ES is
installed) or Qt using OpenGL ES with OpenGL ES installed (regardless of
whether non-ES OpenGL is installed)--but I haven't tested it on an
OpenGL ES compile, so please let me know if you encounter difficulties.

Refs #10336

mythtv/configure

@@ -4183,7 +4183,13 @@ if enabled x11; then
 fi
 
 if enabled x11; then
-    check_libx gl_lib GLES2/gl2.h glClear -lGLESv2 || check_libx gl_lib GL/gl.h glBegin -lGL || check_libx gl_lib GL/gl.h glBegin -lopengl32 || disable opengl
+    if disabled opengles; then
+        # Qt was compiled without OpenGL ES support, so GLES2 isn't usable
+        check_libx gl_lib GL/gl.h glBegin -lGL || check_libx gl_lib GL/gl.h glBegin -lopengl32 || disable opengl
+    else
+        # Qt was compiled with OpenGL ES support, so OpenGL support requires ES
+        check_libx gl_lib GLES2/gl2.h glClear -lGLESv2 || disable opengl
+    fi
 fi
 
 # Quartz video is Mac only and requires Carbon which is 32bit only