Allow most third_party targets to use system libraries if asked.

This extends the pattern in freetype2 to expat, icu, libjpeg-turbo, libpng, libwebp, and zlib, and gives all these an arg to control which to use.

Homebrew doesn't have dng_sdk, piex, or sftnly, or I'd have done the same for them too.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4260

DOCS_PREVIEW= https://skia.org/?cl=4260

Change-Id: I82e780502bf2217336e791787f172a6fc8f55460
Reviewed-on: https://skia-review.googlesource.com/4260
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Hal Canary <halcanary@google.com>

1 files changed, 8 insertions, 10 deletions

diff --git a/third_party/freetype2/BUILD.gn b/third_party/freetype2/BUILD.gn
index 3ac5dd242c..89b64e4ed9 100644
--- a/third_party/freetype2/BUILD.gn
+++ b/third_party/freetype2/BUILD.gn
@@ -4,12 +4,18 @@
 # found in the LICENSE file.
 
 declare_args() {
+  # TODO: false?  i.e. build from source all the time for testing?
+  skia_use_system_freetype2 = !(is_android || sanitize == "MSAN")
 }
 
 import("../third_party.gni")
 
-# TODO: build from source all the time?
-if (is_android || sanitize == "MSAN") {
+if (skia_use_system_freetype2) {
+  system("freetype2") {
+    include_dirs = [ "/usr/include/freetype2" ]
+    libs = [ "freetype" ]
+  }
+} else {
   third_party("freetype2") {
     public_include_dirs = [ "../externals/freetype/include" ]
 
@@ -53,12 +59,4 @@ if (is_android || sanitize == "MSAN") {
       "../externals/freetype/src/truetype/truetype.c",
     ]
   }
-} else {
-  config("system_freetype2") {
-    include_dirs = [ "/usr/include/freetype2" ]
-    libs = [ "freetype" ]
-  }
-  group("freetype2") {
-    public_configs = [ ":system_freetype2" ]
-  }
 }