zig cc: add linker -Map flag

[jiridanek]

Linker maps are a diagnostic/debugging feature. It causes the linker to write out memory ranges (similar to the runtime content of /proc/self/map on Linux) and some such info. I need this because a program I want to compile with zig cc uses this.

Fixes #18356

[jiridanek]

This handles -Map=file which is enough for me. Should -Map file be handled as well?

[jiridanek]

I'm not sure what I'm actually doing here and whether I should do this.

[kubkon]

What is the purpose of this flag in an ELF linker? Additionally, before we consider this for merging, we need a test in test/link/elf.zig with llvm=true and lld=true. Once we move away from lld as the default linker, this will help in narrowing down the missing functionality.

[jiridanek]

@kubkon I could not figure out how to check the .map file content from inside of the test. More importantly, i haven't figured out how to run the test I just wrote (or this test and the least amount of other tests) on my machine

% stage4/bin/zig test ../test/tests.zig --test-filter  testMapFlag
All 0 tests passed.
stage4/bin/zig test ../test/tests.zig --test-filter testMapFlag  4.76s user 1.58s system 100% cpu 6.333 total

Can you or anyone else please suggest how to do both correctly?

[andrewrk]

zig build test-link

You can pass --help to see more options (the help menu is augmented by the contents of build.zig scripts so it's different in different projects).

[andrewrk]

Please see #18356 (comment). @kubkon will be the final word on this, but I think it would be better to not even decide whether to add this functionality until some other things are done. Until then, if you need this feature you will need to use a different toolchain than zig cc. @kubkon please close this pull request if you agree.

[kubkon]

I have to agree with @andrewrk here - this is a new feature request that while may look innocent and easy to implement with LLD in mind, it needs some careful consideration if ported to Zig's linker. Until we decide if we want to accept your proposal, I am closing this PR as not applicable.