mk: tests.mk simplify the method to clean arm testing directory
etc: modify adb_run_wrapper.sh to avoid 'expr' unrecognization at some android devices
etc: add TEST_EXEC_ENV for run-pass to adb_run_wrapper.sh
test: adjust some test cases of run-pass for android
std: fix stat struct of android (SEGV error from run-pass/stat.rs on android)
core -> extra for mac
xfail box-related debug-info tests r=snapshot
ignore inherited environment test under valgrind r=snapshot
_Actually_ xfail debuginfo tests
Remove all #[cfg(stage0)]-protected code

New snapshot means this can all go. Also removes places that have
comments that say they are workarounds for stage0 errors.
libstd: cleanup warnings
libsyntax: cleanup warnings
libextra: cleanup warnings
librust: cleanup warnings (except 1)
Update snapshots.txt
auto merge of #7128 : yichoi/rust/fix_sometc, r=brson

- Fix stat struct for Android (found by SEGV at run-pass/stat.rs)
- Adjust some test cases to rpass for Android 
- Modify some script to rpass for Android