Don't pass -pie when building a shared library build on android

BUG=none
R=ulan@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/822933002

Cr-Commit-Position: refs/heads/master@{#25938}
[turbofan] Turn IrOpcode::Mnemonic() into a table lookup.

R=ishell@chromium.org

Review URL: https://codereview.chromium.org/818203002

Cr-Commit-Position: refs/heads/master@{#25939}
Remove UNREACHABLE() statements from sys-info.cc

We have safe fallbacks in all cases, and it's possible to hit those
codepaths, e.g., on Linux when /proc is not mounted

BUG=v8:3544
R=ulan@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/818213002

Cr-Commit-Position: refs/heads/master@{#25940}