Allow using sanitizers for ssp tests with out-of-tree compiler

[arichardson]

Summary

With an out-of-tree Clang, we can use the -resource-dir flag when linking
to point it at the runtime libraries from the current SYSROOT.
This moves the path to the clang-internal library directory to a separate
.mk file that can be used by Makefiles that want to find the sanitizer
libraries. I intend to re-use this .mk file for my upcoming changes that
allow building the entire base system with ASAN/UBSAN/MSAN.

[dim]

Though I dislike this all getting so complex, I guess there is no good alternative way to get the required information. At some point using an external toolchain will become the default, and then it'd better work... :)

I would really like if there was a way to not always have to pass the resource dir option, though. It seems to be unconditonallly passed now? And I don't think we always want to embed rpaths into executables?

lib/libc/tests/ssp/Makefile

10

Missing dot between 'clang' and 'Otherwise'?

[arichardson]

In D28852#646943, @dim wrote:

Though I dislike this all getting so complex, I guess there is no good alternative way to get the required information. At some point using an external toolchain will become the default, and then it'd better work... :)

I would really like if there was a way to not always have to pass the resource dir option, though. It seems to be unconditonallly passed now? And I don't think we always want to embed rpaths into executables?

I think we should also pass it with the in-tree compiler, otherwise we depend on the compiler install dir containing the sanitizer libraries. Does that even work for universe builds?

[arichardson]

Add missing .

[arichardson]

• Fix incorrect path

[arichardson]

Fix spelling of comments.

[arichardson]

ping?

[dim]

I don't like it too much, but it seems to be necessary to be able to build world with sanitizers later, so let's go for it. :)