Implement sysroot handling

[mati865]

Fixes #406

[mati865]

Right now this handles only linker scripts part based on my guess how it should work. Unfortunately I couldn't find any information in the docs but with this change integration tests fail with errors like:

wild: /home/mateusz/Projects/wild/wild/tests/build/cpp-integration.cc-no-pie-aarch64.wild
ld: /home/mateusz/Projects/wild/wild/tests/build/cpp-integration.cc-no-pie-aarch64.ld
.dynamic.DT_BIND_NOW
  wild
  ld 0x0

.dynamic.DT_FLAGS
  wild 0x8
  ld

So, at least linking is successful.

I still need to fix -L= according to the docs and reconsider if this could be done better.

[davidlattimore]

Thanks for working on this! I tried patching your PR and the tests all passed for me. It's strange that ld isn't setting DT_FLAGS=0x8 (BIND_NOW), given that we should be passing -Wl,-z,now to the compiler when linking.

Boxing a String probably isn't necessary and removing the Box will likely help to eliminate the clippy warning.

[mati865]

Boxing a String probably isn't necessary and removing the Box will likely help to eliminate the clippy warning.

Yeah, it's still WIP. I had started with Path, hence this Box. I haven't touched this since publishing the draft because of other things, but I'll be back to it later today.

[mati865]

So, I searched more extensively, because that sysroot application seemed dangerously broad to me and found where it's described: https://sourceware.org/binutils/docs/ld/File-Commands.html
My guess wasn't that far off, as I missed the condition to use sysroot only when linker script is within the sysroot for absolute paths 😉 Also added = and $SYSROOT handling in the scripts.

This looks mostly good now but still needs some love. I'd like to get your opinion on 556ccc3 (#419) "Is it any better?" commit. I'm not happy with either way, WDYT? Maybe you have a better idea?

Tests and -L= on the CLI are still on my todo list, but probably I'll get to it tomorrow.

[davidlattimore]

So, I searched more extensively, because that sysroot application seemed dangerously broad to me and found where it's described: https://sourceware.org/binutils/docs/ld/File-Commands.html
My guess wasn't that far off, as I missed the condition to use sysroot only when linker script is within the sysroot for absolute paths 😉 Also added = and $SYSROOT handling in the scripts.

Ah, nice find, that makes sense.

This looks mostly good now but still needs some love. I'd like to get your opinion on 556ccc3 (#419) "Is it any better?" commit. I'm not happy with either way, WDYT? Maybe you have a better idea?

Either looks fine to me.

[davidlattimore]

Thanks for taking this on and for figuring out some of the more tricky details involved!