[Flang][OpenMP] Allow zero trait score (llvm#131473)

Author: kiranchandramohan

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

@@ -4969,7 +4969,7 @@ void OmpStructureChecker::CheckTraitSetSelector(
 void OmpStructureChecker::CheckTraitScore(const parser::OmpTraitScore &score) {
   // [6.0:322:23]
   // A score-expression must be a non-negative constant integer expression.
-  if (auto value{GetIntValue(score)}; !value || value <= 0) {
+  if (auto value{GetIntValue(score)}; !value || value < 0) {
     context_.Say(score.source,
         "SCORE expression must be a non-negative constant integer expression"_err_en_US);
   }

flang/test/Semantics/OpenMP/metadirective-common.f90

@@ -21,6 +21,11 @@ subroutine f02
   !$omp & when(user={condition(score(-2): .true.)}: nothing)
 end
 
+subroutine f02_zero_score
+  !$omp metadirective &
+  !$omp & when(user={condition(score(0): .true.)}: nothing)
+end
+
 subroutine f03(x)
   integer :: x
   !$omp metadirective &