[clang] [compiler-rt] [safestack] Support statically linked executables (PR #190126)

[Jakob Koschel via cfe-commits]

jakos-sec wrote:

Thank you for the PR! I've just tested this and the only thing to keep in mind is e.g. using a custom allocator (or any safestack instrumented code within `_dl_non_dynamic_init()`). Since in the static binary there can be quite a bit of code running before `.preinit_array` is called to initialize safestack.

https://github.com/llvm/llvm-project/pull/190126