This is the third stage of 05356e35
and is necessary for projects putting use_libpci in the gn args, like
headless Chrome.

BUG=angleproject:1874

Change-Id: I03a010ababf08f992f0fb26ff87ddc48afd5a237
Reviewed-on: https://chromium-review.googlesource.com/457277Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>