Use standard location for default mips linux sysroot
The mips sysroot is automatically installed in this
location by gclient hooks (install-debian.wheezy.sysroot.py).
Expect mipsel-linux-gcc to be in the PATH rather than
finding it relative to the sysroot. This matches the
behaviour the arm linux cross compile.
Depends on this native_client change: https://codereview.chromium.org/
1212573002
BUG=504471
TEST=build all with target_arch=mips
Review URL: https://codereview.chromium.org/
1207323003
Cr-Commit-Position: refs/heads/master@{#339945}