[GN] Fix generate Xcode project for macOS to work with Xcode 8.

Overridding ARCHS prevents Xcode 8+ from running the compiled binary
on macOS. In addition avoid hard-coding the version of the SDK to use
(since we do not build with Xcode this value is unused) and instead
mention that the version-less SDK.

BUG=634501

Review-Url: https://codereview.chromium.org/2542613002
Cr-Original-Commit-Position: refs/heads/master@{#435483}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5d7f4cee65382c428e9d08112354a8a9bd496aa9
1 file changed
tree: a2f76caa599ce4ce7abf3d5cdaf76d28f4254427
  1. tools/