This is useful for people using Dawn's standalone build to compile
static libraries to use in other projects. Without this static libraries
will act as source sets as is GN's default.
BUG=dawn:85
Change-Id: I4d99cbbbe67c73f226717651cb12ed0a172409b2
Reviewed-on: https://dawn-review.googlesource.com/c/3840
Reviewed-by: Stephen White <senorblanco@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>