[flang] Catch both EXTERNAL and INTRINSIC on type declaration stmt (#150254)

The EXTERNAL and INTRINSIC attributes can't both appear on the same type
declarations statement.

Fixes llvm/llvm-project#149771.

Author: klausler

flang/lib/Semantics/resolve-names.cpp

@@ -2351,7 +2351,8 @@ bool AttrsVisitor::IsConflictingAttr(Attr attrName) {
       HaveAttrConflict(attrName, Attr::PASS, Attr::NOPASS) || // C781
       HaveAttrConflict(attrName, Attr::PURE, Attr::IMPURE) ||
       HaveAttrConflict(attrName, Attr::PUBLIC, Attr::PRIVATE) ||
-      HaveAttrConflict(attrName, Attr::RECURSIVE, Attr::NON_RECURSIVE);
+      HaveAttrConflict(attrName, Attr::RECURSIVE, Attr::NON_RECURSIVE) ||
+      HaveAttrConflict(attrName, Attr::INTRINSIC, Attr::EXTERNAL);
 }
 bool AttrsVisitor::CheckAndSet(Attr attrName) {
   if (IsConflictingAttr(attrName) || IsDuplicateAttr(attrName)) {

flang/test/Semantics/resolve126.f90

@@ -0,0 +1,7 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+!ERROR: Attributes 'INTRINSIC' and 'EXTERNAL' conflict with each other
+real, external, intrinsic :: exp
+!ERROR: Symbol 'sin' cannot have both EXTERNAL and INTRINSIC attributes
+external sin
+intrinsic sin
+end