[Driver] Do not generate error about unsupported target specific options when there is no compiler jobs

The upstream commit: https://reviews.llvm.org/D151590
added a new flag to mark target specific compiler options.

The side effect of it was that in cases when -### or -v is used without any
input file, clang started emitting an error.
It happened like that becasue there is no compilation actions created
which could consume/verify these target specific options.

This patch changes that error to a warning about unused option in situations
when there is no actions and still generates error when there are actions.

Fix for #64958

Differential Revision: https://reviews.llvm.org/D159361

Author: mgabka

clang/lib/Driver/Driver.cpp

@@ -4953,7 +4953,12 @@ void Driver::BuildJobs(Compilation &C) const {
       // already been warned about.
       if (!IsCLMode() || !A->getOption().matches(options::OPT_UNKNOWN)) {
         if (A->getOption().hasFlag(options::TargetSpecific) &&
-            !A->isIgnoredTargetSpecific() && !HasAssembleJob) {
+            !A->isIgnoredTargetSpecific() && !HasAssembleJob &&
+            // When for example -### or -v is used
+            // without a file, target specific options are not
+            // consumed/validated.
+            // Instead emitting an error emit a warning instead.
+            !C.getActions().empty()) {
           Diag(diag::err_drv_unsupported_opt_for_target)
               << A->getSpelling() << getTargetTriple();
         } else {

clang/test/Driver/no-action.c

@@ -0,0 +1,10 @@
+// RUN: %clang --target=aarch64-none-gnu --verbose -mcpu= -march= 2>&1 | FileCheck %s --check-prefix=WARNING
+// RUN: %clang --target=aarch64-none-gnu -### -mcpu= -march= 2>&1 | FileCheck %s --check-prefix=WARNING
+
+// RUN: %clang --target=x86_64-unknown-linux-gnu --verbose -mcpu= -march= 2>&1 | FileCheck %s --check-prefix=WARNING
+// RUN: %clang --target=x86_64-unknown-linux-gnu -### -mcpu= -march= 2>&1 | FileCheck %s --check-prefix=WARNING
+
+/// In situation when there is no compilation/linking clang should not emit error
+/// about target specific options, but just warn that are not used.
+WARNING: warning: argument unused during compilation
+WARNING: warning: argument unused during compilation