Remove obsolete OS handling in GN.

There was a a bunch of built-in special-casing of the current_os variable which has been gradually removed over time as we have needed extra flexibility and reduced special casing.

The only use of this was for libs ending in .framework on Mac. I think it's OK to run the special-casing on all OS's, since in pracice libraries on Windows and Linux can't end in ".framework".

A bunch of setup and maintenance of these variables is removed.

Review URL: https://codereview.chromium.org/1431323003

Cr-Original-Commit-Position: refs/heads/master@{#359170}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d4f9637d51829c0d779e7ce07b945e8b7813397d
8 files changed
tree: 866ca06b1db69a2c6c47a903e88b2963b60c3674
  1. tools/