Fix usage of find_package(OpenGL) on Linux (#1733)

Fixes #1731

cmake/libigl.cmake

@@ -350,12 +350,11 @@ if(LIBIGL_WITH_OPENGL)
   if (NOT CMAKE_VERSION VERSION_LESS "3.11")
     cmake_policy(SET CMP0072 NEW)
   endif()
-  find_package(OpenGL REQUIRED)
-  if(TARGET OpenGL::GL)
-    target_link_libraries(igl_opengl ${IGL_SCOPE} OpenGL::GL)
+  find_package(OpenGL REQUIRED OPTIONAL_COMPONENTS OpenGL)
+  if(TARGET OpenGL::OpenGL)
+    target_link_libraries(igl_opengl ${IGL_SCOPE} OpenGL::OpenGL)
   else()
-    target_link_libraries(igl_opengl ${IGL_SCOPE} ${OPENGL_gl_LIBRARY})
-    target_include_directories(igl_opengl SYSTEM ${IGL_SCOPE} ${OPENGL_INCLUDE_DIR})
+    target_link_libraries(igl_opengl ${IGL_SCOPE} OpenGL::GL)
   endif()
 
   # glad module