[lld/mac] Stop accepting arbitrary suffixes on --(no-)warn-dylib-install-name

[thakis]

Summary

The flag accidentally used Joined<> instead of Flag<>.

Previously, --warn-dylib-install-namefoobarbaz would be accepted and
had the same effect as -warn-dylib-install-name. Now the flag only
works if no suffix is attached to it, as originally intended.

Also fix a typo in the flag's help text.

[thakis]

Noticed this while reading Options.td.

Adding a test for this doesn't seem terribly valuable, so I decided against it.

[thakis]

fix typo too

[MaskRay]

LGTM.

[thevinster]

Whoops, this might've been a copy paste error on my end. Thanks for catching it!

lld/MachO/Options.td

def thinlto_cache_policy_eq: Joined<["--"], "thinlto-cache-policy=">,
     HelpText<"Pruning policy for the ThinLTO cache">,
     Group<grp_lld>;
 def O : JoinedOrSeparate<["-"], "O">,
     HelpText<"Optimize output file size">;
 def start_lib: Flag<["--"], "start-lib">,
     HelpText<"Start a grouping of objects that should be treated as if they were together in an archive">;
 def end_lib: Flag<["--"], "end-lib">,
     HelpText<"End a grouping of objects that should be treated as if they were together in an archive">;
-def no_warn_dylib_install_name: Joined<["--"], "no-warn-dylib-install-name">,
-    HelpText<"Do not warn on -install-name if -dylib is not passed (default)">,
+def no_warn_dylib_install_name: Flag<["--"], "no-warn-dylib-install-name">,
+    HelpText<"Do not warn on -install_name if -dylib is not passed (default)">,
     Group<grp_lld>;
-def warn_dylib_install_name: Joined<["--"], "warn-dylib-install-name">,
-    HelpText<"Warn on -install-name if -dylib is not passed">,
+def warn_dylib_install_name: Flag<["--"], "warn-dylib-install-name">,
+    HelpText<"Warn on -install_name if -dylib is not passed">,
     Group<grp_lld>;
 def call_graph_profile_sort: Flag<["--"], "call-graph-profile-sort">,
     HelpText<"Reorder sections with call graph profile (default)">,
     Group<grp_lld>;
 def no_call_graph_profile_sort : Flag<["--"], "no-call-graph-profile-sort">,
     HelpText<"Do not reorder sections with call graph profile">,
     Group<grp_lld>;
 def print_symbol_order_eq: Joined<["--"], "print-symbol-order=">,