[compiler-rt] [asan] Ignore vDSO on FreeBSD (PR #76223)

[Dimitry Andric via llvm-commits]

DimitryAndric wrote:

Btw on 15-CURRENT I can apply this patch, and then indeed I don't get "ASan runtime does not come first in initial library list" anymore, but another assertion failure instead:

```text
$  ldd ./asantest-shared
./asantest-shared:
        libclang_rt.asan-x86_64.so => /usr/lib/clang/17/lib/freebsd/libclang_rt.asan-x86_64.so (0xc369bfd000)
        libc.so.7 => /lib/libc.so.7 (0xc368118000)
        libc++.so.1 => /lib/libc++.so.1 (0xc368f43000)
        libcxxrt.so.1 => /lib/libcxxrt.so.1 (0xc36b186000)
        libm.so.5 => /lib/libm.so.5 (0xc36c555000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xc36bdb2000)
        [vdso] (0xc3678f6000)

$ ./asantest-shared
AddressSanitizer: CHECK failed: asan_posix.cpp:121 "((0)) == ((pthread_key_create(&tsd_key, destructor)))" (0x0, 0x4e) (tid=100239)
    <empty stack>
```

So I'm not going to cherry-pick now, until I can figure out why it still fails.

https://github.com/llvm/llvm-project/pull/76223