sdl12-compat: cmake: fixed silly mistake

SDL Commits
1 
From 25ae1571ce84af4144ad5ea8380f39bd026ee0fb Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 10 Jun 2021 14:43:59 -0400
Subject: [PATCH] cmake: fixed silly mistake

---
 CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0744f9c..82c3017 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -98,8 +98,8 @@ if(SDL12TESTS)
     if(OpenGL_FOUND)
       set(HAVE_OPENGL_DEFINE "HAVE_OPENGL")
       if(WIN32)
-        set(${OPENGL_gl_LIBRARY} "OpenGL32")
-        set(${OPENGL_opengl_LIBRARY} "OpenGL32")
+        set(OPENGL_gl_LIBRARY "OpenGL32")
+        set(OPENGL_opengl_LIBRARY "OpenGL32")
       endif()
     endif()