FEX/Config: Allow override of cache location

This will be used.

Source/Common/Config.cpp

@@ -603,6 +603,11 @@ fextl::string GetConfigDirectory(bool Global, const PortableInformation& Portabl
 }
 
 fextl::string GetCacheDirectory() {
+  const char* CacheOverride = getenv("FEX_APP_CACHE_LOCATION");
+  if (CacheOverride) {
+    return CacheOverride;
+  }
+
   const char* HomeDir = GetHomeDirectory();
   const char* CacheXDG = getenv("XDG_CACHE_HOME");
   return (CacheXDG ? fextl::string {CacheXDG} : (fextl::string {HomeDir} + "/.cache")) + "/fex-emu/";