Revert of [iOS] Defaults to use system libjpeg on iOS.

third_party/BUILD.gn

Index: third_party/BUILD.gn
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index 6d97aafdbce05c75ea1a3ed68552d77ba115b94e..cf62b83fca29975a1817d3791b0110c2cf9250a0 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -8,7 +8,7 @@
 
 declare_args() {
   # Uses system libjpeg. If true, overrides use_libjpeg_turbo.
-  use_system_libjpeg = is_ios
+  use_system_libjpeg = false
 
   # Uses libjpeg_turbo as the jpeg implementation. Has no effect if
   # use_system_libjpeg is set.
@@ -16,7 +16,6 @@
 }
 
 config("system_libjpeg_config") {
-  libs = [ "jpeg" ]
   defines = [ "USE_SYSTEM_LIBJPEG" ]
 }
 
@@ -29,6 +28,7 @@
 # declared in this file.
 group("jpeg") {
   if (use_system_libjpeg) {
+    libs = [ "jpeg" ]
     public_configs = [ ":system_libjpeg_config" ]
   } else if (use_libjpeg_turbo) {
     public_deps = [