Fixed bug 4643 - Append EGL CFLAGS in CheckOpenGLESX11

Danilo Spinella

EGL need -DMESA_EGL_NO_X11_HEADERS in systems without X11 installed. Make CMake checks import EGL CFLAGS.

Relevant bug: https://bugzilla.libsdl.org/show_bug.cgi?id=4243

cmake/sdlchecks.cmake

@@ -757,8 +757,10 @@ macro(CheckOpenGLX11)
 endmacro()
 
 # Requires:
-# - nada
+# - PkgCheckModules
 macro(CheckOpenGLESX11)
+  pkg_check_modules(EGL egl)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${EGL_CFLAGS}")
   if(VIDEO_OPENGLES)
     check_c_source_compiles("
         #define EGL_API_FB