SDL: cmake: FindOpenGL.cmake shipped by emscripten does not have OpenGL::GL

SDL Commits
1 
From cfa76973ff446b3f9a9909be90a140edf3566e42 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Tue, 1 Nov 2022 11:33:39 +0100
Subject: [PATCH] cmake: FindOpenGL.cmake shipped by emscripten does not have
 OpenGL::GL

---
 test/CMakeLists.txt | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index d89be52b08d3..f358b039b35f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -226,8 +226,14 @@ if(SDL_DUMMYVIDEO)
 endif()
 
 if(OPENGL_FOUND)
-    target_link_libraries(testshader OpenGL::GL)
-    target_link_libraries(testgl2 OpenGL::GL)
+    if(TARGET OpenGL::GL)
+        target_link_libraries(testshader OpenGL::GL)
+        target_link_libraries(testgl2 OpenGL::GL)
+    else()
+        # emscripten's FindOpenGL.cmake does not create OpenGL::GL
+        target_link_libraries(testshader ${OPENGL_gl_LIBRARY})
+        target_link_libraries(testgl2 ${OPENGL_gl_LIBRARY})
+    endif()
 endif()
 
 file(GLOB RESOURCE_FILES *.bmp *.wav *.hex moose.dat utf8.txt)