[libunwind] [Libunwind] Try to fix msan failures (PR #120013)

[Dmitry Chestnykh via cfe-commits]

chestnykh wrote:

Maybe load order breaks something:
With `-lunwind` passed explicitly:
```
        linux-vdso.so.1 (0x0000700799647000)
        libunwind.so.1 => /usr/lib/libunwind.so.1 (0x00007007995fe000)
        libatomic.so.1 => /usr/lib/libatomic.so.1 (0x00007007995f3000)
        libc++.so.1 => /usr/lib/libc++.so.1 (0x00007007994ec000)
        libc++abi.so.1 => /usr/lib/libc++abi.so.1 (0x00007007949c0000)
        libm.so.6 => /usr/lib/libm.so.6 (0x00007007948d1000)
        libresolv.so.2 => /usr/lib/libresolv.so.2 (0x00007007948bf000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007007946ce000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007007946a0000)
        /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x0000700799649000)
```

With only `-rtlib=compiler-rt -unwindlib=libunwind` (without explicit `-lunwind` in the driver cmdline)
```
        linux-vdso.so.1 (0x000077ed1ce4a000)
        libunwind.so.1 => /usr/lib/libunwind.so.1 (0x000077ed1ce01000)
        libatomic.so.1 => /usr/lib/libatomic.so.1 (0x000077ed1cdf6000)
        libc++.so.1 => /usr/lib/libc++.so.1 (0x000077ed1ccef000)
        libc++abi.so.1 => /usr/lib/libc++abi.so.1 (0x000077ed181c0000)
        libm.so.6 => /usr/lib/libm.so.6 (0x000077ed180d1000)
        libresolv.so.2 => /usr/lib/libresolv.so.2 (0x000077ed180bf000)
        libc.so.6 => /usr/lib/libc.so.6 (0x000077ed17ece000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x000077ed17ea0000)
        /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x000077ed1ce4c000)
```

https://github.com/llvm/llvm-project/pull/120013