Add objc_compile to compile_actions

The majority of the time objc_compile is identical to C/C++ compiles.
Because of this I think by default all of those flags should apply here.
This is a bit funny since the current builtin toolchain doesn't support
Objective-C at all and that's only in the apple_support toolchain, but
new toolchains using these rules may want to support this.

Without this things like `--objccopt` just don't work out of the box.

cc/toolchains/actions/BUILD

@@ -210,6 +210,7 @@ cc_action_type_set(
         ":cpp_compile_actions",
         ":c_compile_actions",
         ":assembly_actions",
+        ":objc_compile",
     ],
 )