[flang][Semantics] Testcase for declaration conflict with named-construct

Author: kparzysz

flang/test/Semantics/named-construct-declaration-conflict.f90

@@ -0,0 +1,10 @@
+!RUN: %python %S/test_errors.py %s %flang_fc1
+
+subroutine foo()
+  integer :: nxloop
+!ERROR: 'nxloop' is already declared in this scoping unit
+  nxloop: do i = 1, 100
+  enddo nxloop
+end subroutine
+
+