[clang] [OpenACC] Implement 'cache' construct parsing (PR #74324)

[via cfe-commits]

================
@@ -268,6 +270,71 @@ ExprResult Parser::ParseOpenACCRoutineName() {
   return getActions().CorrectDelayedTyposInExpr(Res);
 }
 
+void Parser::ParseOpenACCCacheVar() {
----------------
cor3ntin wrote:

Maybe it would be nice to do like C and C++, ie citing the standard + grammar production in a comment

https://github.com/llvm/llvm-project/pull/74324