[sanitizers] do not add -lclang_rt on mac.
[sanitizers] do not add -lclang_rt on mac.

Clang frontend adds appropriate -l options automatically depending
on -fsanitize value.

BUG=597066

Review-Url: https://codereview.chromium.org/1948873002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#391578}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk