[flang] [llvm] [Flang][OpenMP] Add semantic checks for Worshare construct (PR #111358)

[Tom Eccles via llvm-commits]

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@@ -1162,7 +1162,7 @@ def OMP_Workshare : Directive<"workshare"> {
   let category = CA_Executable;
 }
 def OMP_EndWorkshare : Directive<"end workshare"> {
-  let allowedClauses = [
+  let allowedOnceClauses = [
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tblah wrote:

nit: please could you add a test for this check as well. Something in `flang/test/` is okay

Otherwise this LGTM

https://github.com/llvm/llvm-project/pull/111358