[Caching] Move frontend-parseable-output into cache invariant group

`frontend-parseable-output` related options only affects diagnostics and
should be cache invariant. This also fixes the bug that xcbuild can
sometimes modify this argument from execution pipeline, causing cache
key to change.

rdar://120552768

Author: cachemeifyoucan

include/swift/Option/FrontendOptions.td

@@ -77,6 +77,9 @@ def backup_module_interface_path_EQ :
   Joined<["-"], "backup-module-interface-path=">,
   Alias<backup_module_interface_path>;
 
+def frontend_parseable_output : Flag<["-"], "frontend-parseable-output">,
+  HelpText<"Emit textual output in a parseable format">;
+
 } // end let Flags = [FrontendOption, NoDriverOption, CacheInvariant]
 
 def primary_file : Separate<["-"], "primary-file">,
@@ -87,9 +90,6 @@ let Flags = [FrontendOption, NoDriverOption] in {
 
 def triple : Separate<["-"], "triple">, Alias<target>;
 
-def frontend_parseable_output : Flag<["-"], "frontend-parseable-output">,
-  HelpText<"Emit textual output in a parseable format">;
-
 def emit_module_doc : Flag<["-"], "emit-module-doc">,
   HelpText<"Emit a module documentation file based on documentation "
            "comments">;

include/swift/Option/Options.td

@@ -1801,7 +1801,7 @@ def emit_module_dependencies_path:
 
 def use_frontend_parseable_output:
   Flag<["-"], "use-frontend-parseable-output">,
-  Flags<[HelpHidden, NewDriverOnlyOption]>,
+  Flags<[HelpHidden, NewDriverOnlyOption, CacheInvariant]>,
   HelpText<"Emit parseable-output from swift-frontend jobs instead of from "
            "the driver">;