[sanitizer] mmap2 syscall works with 4096-byte units instead of bytes.

Ouch.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224819 91177308-0d34-0410-b5e6-96231b3b80d8
[sanitizer] Disable InternalMmapWithOffset test on Windows.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224820 91177308-0d34-0410-b5e6-96231b3b80d8