lld: ignore the `-search_paths_first` option on MachO

[compnerd]

Summary

ld64 provides the -search_path_firsts which will search each path in
the library search path order for both lib[name].dylib, lib[name].a
before moving on (searching all paths for the dylib and then falling
back to the static library if a shared library was not found).

This option has been the default for a long time, but the command line
flag still exists. Ignore it for compatibility.

[smeenai]

@gkm is working on larger-scale ld64 option handling in D80582, but this looks good to go in in the meantime.

[smeenai]

Although, fun fact, our handling for -l doesn't search for static libraries at all right now :D That's definitely something to fix.

[compnerd]

rG37d93b528c1

As to the fun fact: 😒 ... thanks for pointing it out though, definitely something to track (which I guess raises the question of, is there any tracking for all the items that are still to do?)

[int3]

is there any tracking for all the items that are still to do?

Just in the form of TODO comments (there isn't one for the abovementioned though)

lld/MachO/Options.td

 def: Flag<["-"], "demangle">;
 def: Flag<["-"], "dynamic">;
 def: Flag<["-"], "no_deduplicate">;
+def: Flag<["-"], "search_paths_first">;
 def platform_version: Flag<["-"], "platform_version">;
 def: Separate<["-"], "lto_library">;
 def: Separate<["-"], "macosx_version_min">;