[sanitizer_common] Fix Posix/mmap_write_exec.cpp on 32-bit Solaris

The new `Posix/mmap_write_exec.cpp` test FAILs on 32-bit Solaris/x86.  This
happens because only `mmap` is intercepted, but not `mmap64` which is used
for largefile support.

Fixed by also intercepting `mmap64`.

Tested on `amd64-pc-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D112810