[asan][test] XFAIL Posix/no_asan_gen_globals.c on Solaris

`Posix/no_asan_gen_globals.c` currently `FAIL`s on Solaris:

  $ nm no_asan_gen_globals.c.tmp.exe | grep ___asan_gen_
  0809696a r .L___asan_gen_.1
  0809a4cd r .L___asan_gen_.2
  080908e2 r .L___asan_gen_.4
  0809a4cd r .L___asan_gen_.5
  0809a529 r .L___asan_gen_.7
  0809a4cd r .L___asan_gen_.8

As detailed in Bug 47607, there are two factors here:

- `clang` plays games by emitting some local labels into the symbol
  table.  When instead one uses `-fno-integrated-as` to have `gas` create
  the object files, they don't land in the objects in the first place.
- Unlike GNU `ld`, the Solaris `ld` doesn't support support
  `-X`/`--discard-locals` but instead relies on the assembler to follow its
  specification and not emit local labels.

Therefore this patch `XFAIL`s the test on Solaris.

Tested on `amd64-pc-solaris2.11` and `x86_64-pc-linux-gnu`.

Differential Revision: https://reviews.llvm.org/D88218