[compiler-rt] [dfsan] Re-exec with no ASLR if memory layout is incompatible on Linux (PR #85674)

[Thurston Dang via llvm-commits]

thurstond wrote:

> (looks right to me and if this passes tests with the ASLR change then lgtm)

Thanks for the review!

The test results are better with this patch.

At any ASLR entropy setting, custom.cpp fails with or without this patch.

With 32 bits of ASLR entropy:
- before this patch: there's 31 additional tests (including release_shadow_space.c) that fail
- after this patch: 1 test (release_shadow_space.c) occasionally fails, but I think it's a flaky test that needs adjustment to the margin of error (`Assertion 'after_fixed_mmap <= before + delta + mmap_origin_chain_kb' failed`; "The assert checks the memory up to a delta."). In any case, this test fails before the patch, so this patch is an improvement.

https://github.com/llvm/llvm-project/pull/85674