commit 691bfec9d73bfefae30bad32e7a6496f2beceb9c
author Tom Anderson <thomasanderson@chromium.org> Wed Jul 25 18:30:59 2018
committer Tom Anderson <thomasanderson@chromium.org> Wed Jul 25 18:30:59 2018
tree 25c28a4b25713d5e6ffd79e43142bdedecdd5335
parent 5a265b45c14ce064b8174fcde86189b872c6efc8

Only set is_component_build if !is_component_build

It's necessary to prevent this error:

ERROR at //buildtools/third_party/libc++/BUILD.gn:22:27: Assignment had no effect.
  static_component_type = "source_set"
                          ^-----------
You set the variable "static_component_type" here and it was unused before it went
out of scope.
See //build/config/BUILDCONFIG.gn:702:3: whence it was called.
  target(_component_mode, target_name) {
  ^-------------------------------------
See //buildtools/third_party/libc++/BUILD.gn:21:1: whence it was called.
component("libc++") {
^--------------------
See //third_party/catapult/devil/BUILD.gn:18:5: which caused the file to be included.
    "//buildtools/third_party/libc++($host_toolchain)",
    ^-------------------------------------------------

TBR=pcc

Change-Id: I193ca6d023405d8295a24a2a7a8d5712b73e5887