Improve GN asmflags help.

Hooks up asmflags to the "gn help" overview (the INSERT_VARIABLE line was missing). Reference asmflags from the cflag help, and include flag ordering information on the asmflags help.

Review URL: https://codereview.chromium.org/1489683002

Cr-Original-Commit-Position: refs/heads/master@{#362279}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: fde26f231be483ca7b25d89503e0c76ff70cda97
1 file changed
tree: a708017d7370fca68ed49302d4ae31050c527736
  1. tools/