[clang][ARM] Re-word PACBTI warning.

The original warning added in D115501 when pacbti is used with an
incompatible architecture was not exactly correct because it was
not really ignored and can affect codegen.

Therefore reword to say that the pacbti option is incompatible with
the given architecture.

Reviewed By: chill

Differential Revision: https://reviews.llvm.org/D119166

Author: amilendra

clang/include/clang/Basic/DiagnosticCommonKinds.td

@@ -145,8 +145,8 @@ def warn_conflicting_nullability_attr_overriding_param_types : Warning<
 def err_nullability_conflicting : Error<
   "nullability specifier %0 conflicts with existing specifier %1">;
 
-def warn_target_unsupported_branch_protection_option: Warning <
-  "ignoring '-mbranch-protection=' option because the '%0' architecture does not support it">,
+def warn_incompatible_branch_protection_option: Warning <
+  "'-mbranch-protection=' option is incompatible with the '%0' architecture">,
   InGroup<BranchProtection>;
 
 def warn_target_unsupported_branch_protection_attribute: Warning <

clang/lib/Driver/ToolChains/Clang.cpp

@@ -1639,7 +1639,7 @@ static void CollectARMPACBTIOptions(const ToolChain &TC, const ArgList &Args,
   const Driver &D = TC.getDriver();
   const llvm::Triple &Triple = TC.getEffectiveTriple();
   if (!(isAArch64 || (Triple.isArmT32() && Triple.isArmMClass())))
-    D.Diag(diag::warn_target_unsupported_branch_protection_option)
+    D.Diag(diag::warn_incompatible_branch_protection_option)
         << Triple.getArchName();
 
   StringRef Scope, Key;

clang/test/Driver/arm-security-options.c

@@ -90,4 +90,4 @@
 // BAD-B-KEY-COMBINATION: invalid branch protection option 'b-key' in '-mbranch-protection={{.*}}'
 // BAD-LEAF-COMBINATION: invalid branch protection option 'leaf' in '-mbranch-protection={{.*}}'
 
-// INCOMPATIBLE-ARCH: ignoring '-mbranch-protection=' option because the '{{.*}}' architecture does not support it
+// INCOMPATIBLE-ARCH: '-mbranch-protection=' option is incompatible with the '{{.*}}' architecture