[Driver] Give warn_drv_include_probe_gch a dedicated flag

See discussion on #67084

Author: zmodem

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -433,7 +433,7 @@ def warn_drv_treating_input_as_cxx : Warning<
   InGroup<Deprecated>;
 def warn_drv_include_probe_gch : Warning<
   "'%0' probing .gch is deprecated. Use '-include-pch %1' or switch to .pch instead">,
-  InGroup<Deprecated>;
+  InGroup<DeprecatedIncludeGch>;
 def warn_drv_pch_not_first_include : Warning<
   "precompiled header '%0' was ignored because '%1' is not first '-include'">;
 def warn_missing_sysroot : Warning<"no such sysroot directory: '%0'">,

clang/include/clang/Basic/DiagnosticGroups.td

@@ -209,6 +209,7 @@ def DeprecatedWritableStr : DiagGroup<"deprecated-writable-strings",
                                       [CXX11CompatDeprecatedWritableStr]>;
 def DeprecatedPragma : DiagGroup<"deprecated-pragma">;
 def DeprecatedType : DiagGroup<"deprecated-type">;
+def DeprecatedIncludeGch : DiagGroup<"deprecated-include-gch">;
 // FIXME: Why is DeprecatedImplementations not in this group?
 def Deprecated : DiagGroup<"deprecated", [DeprecatedAnonEnumEnumConversion,
                                           DeprecatedArrayCompare,
@@ -232,6 +233,7 @@ def Deprecated : DiagGroup<"deprecated", [DeprecatedAnonEnumEnumConversion,
                                           DeprecatedVolatile,
                                           DeprecatedWritableStr,
                                           DeprecatedRedundantConstexprStaticDef,
+                                          DeprecatedIncludeGch
                                           ]>,
                  DiagCategory<"Deprecations">;