Test process::tests::test_inherit_env fails on Windows (GNU)

[petrochenkov]

Windows 8.1 64-bit / MSYS2 / MinGW-w64

thread '<unnamed>' panicked at 'output doesn't contain `=C:=C:\Windows\System32`
!;=;\
ACLOCAL_PATH=C:\msys64\mingw64\share\aclocal;C:\msys64\usr\share\aclocal
ALLUSERSPROFILE=C:\ProgramData
APPDATA=C:\Users\we\AppData\Roaming
...
_=x86_64-pc-windows-gnu/stage2/test/stdtest-x86_64-pc-windows-gnu.exe
temp=C:\Users\we\AppData\Local\Temp
tmp=C:\Users\we\AppData\Local\Temp
', src/libstd\process.rs:807
test process::tests::test_inherit_env ... FAILED

cc @tbu-