Pull GN binary at r275833

Also fixes some build errors on non-Linux platforms.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/323643004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276063 0039d316-1c4b-4281-b951-d872f2087c98

• build/config/compiler/BUILD.gn[diff]
• net/BUILD.gn[diff]
• tools/gn/bin/linux/gn.sha1[diff]
• tools/gn/bin/linux/gn32.sha1[diff]
• tools/gn/bin/mac/gn.sha1[diff]
• tools/gn/bin/win/gn.exe.sha1[diff]
• ui/aura/BUILD.gn[diff]