[flang] Add new semantics tests for `unlock-stmt`

[samdsilvaa]

Summary

Add two semantics tests for unlock-stmt, one with standard-conforming
and one with non-standard conforming statements

[ktras]

LGTM. @samdsilvaa, I don't believe you have push permissions, would you like me to push on your behalf?

[samdsilvaa]

Yes please, thank you!

flang/test/Semantics/unlockstmt01.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1
+program test_unlock_stmt
+
+  use iso_fortran_env, only: lock_type
+
+  type(LOCK_TYPE) :: myLock[*], locks(10)[*]
+  integer :: stat_variable
+  character(len = 128) :: errmsg_variable
+
+  !___ standard-conforming statements ___
+  UNLOCK(myLock)
+  UNLOCK(locks(3))
+  Unlock(locks(1), stat = stat_variable)
+  Unlock(locks(2), ERRMSG = errmsg_variable)
+  Unlock(locks(4), stat = stat_variable, ERRMSG = errmsg_variable)
+end program test_unlock_stmt

flang/test/Semantics/unlockstmt02.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1
+! XFAIL: *
+program test_unlock_stmt
+
+  use iso_fortran_env, only: lock_type
+
+  type(LOCK_TYPE) :: locks(10)[*]
+  integer :: non_lock
+
+  !ERROR: TBD
+  type(LOCK_TYPE) :: non_coarray !Invalid Declaration
+
+  !___ non-standard-conforming statements ___
+
+  !ERROR: TBD
+  UNLOCK(non_lock)
+  !ERROR: Must be a scalar value, but is a rank-1 array
+  UNLOCK(locks)
+
+ !Sync-stat-list.f90 contains invalid versions of sync-stat-list in unlock-stmt
+
+end program test_unlock_stmt