Fix threadprivate variable scope inside BLOCK construct. (#88921)

When a local variable inside a BLOCK construct is used as threadprivate
variable, llvm-flang throws below error:

> error: The THREADPRIVATE directive and the common block or variable in
it must appear in the same declaration section of a scoping unit

Author: harishch4

flang/lib/Semantics/check-omp-structure.cpp

@@ -1048,7 +1048,7 @@ void OmpStructureChecker::CheckThreadprivateOrDeclareTargetVar(
                       name->symbol->GetUltimate().owner();
                   if (!curScope.IsTopLevel()) {
                     const semantics::Scope &declScope =
-                        GetProgramUnitContaining(curScope);
+                        GetProgramUnitOrBlockConstructContaining(curScope);
                     const semantics::Symbol *sym{
                         declScope.parent().FindSymbol(name->symbol->name())};
                     if (sym &&

flang/test/Lower/OpenMP/threadprivate-hlfir.f90

@@ -24,3 +24,4 @@ subroutine sub()
     print *, a
   !$omp end parallel
 end subroutine
+

flang/test/Semantics/OpenMP/threadprivate07.f90

@@ -0,0 +1,15 @@
+! RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+
+! Check Threadprivate Directive with local variable of a BLOCK construct.
+
+program main
+  call sub1()
+  print *, 'pass'
+end program main
+
+subroutine sub1()
+  BLOCK
+    integer, save :: a
+    !$omp threadprivate(a)
+  END BLOCK
+end subroutine