[Sanitizer] Write a slightly better implementation of GetEnv() function on Windows

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@177051 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Intercept __strdup, strndup, __strndup.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@177052 91177308-0d34-0410-b5e6-96231b3b80d8