[OPENMP]Fix PR43771: Do not capture contexprs variables.

If the variable is a constexpr variable, it should not be captured in the OpenMP region.
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index c7e0d2a..8b1fca8 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -1894,6 +1894,11 @@
   assert(LangOpts.OpenMP && "OpenMP is not allowed");
   D = getCanonicalDecl(D);
 
+  auto *VD = dyn_cast<VarDecl>(D);
+  // Do not capture constexpr variables.
+  if (VD && VD->isConstexpr())
+    return nullptr;
+
   // If we want to determine whether the variable should be captured from the
   // perspective of the current capturing scope, and we've already left all the
   // capturing scopes of the top directive on the stack, check from the
@@ -1904,7 +1909,6 @@
   // If we are attempting to capture a global variable in a directive with
   // 'target' we return true so that this global is also mapped to the device.
   //
-  auto *VD = dyn_cast<VarDecl>(D);
   if (VD && !VD->hasLocalStorage() &&
       (getCurCapturedRegion() || getCurBlock() || getCurLambda())) {
     if (isInOpenMPDeclareTargetContext()) {