GN(android) Don't enable --gc-sections in debug mode.

chrome/BUILD.gn

Index: chrome/BUILD.gn
diff --git a/chrome/BUILD.gn b/chrome/BUILD.gn
index d741423927b7be6f43066f886ab28e632f22942b..b7481faad874330641d2ddae8373603c5b302f2f 100644
--- a/chrome/BUILD.gn
+++ b/chrome/BUILD.gn
@@ -962,8 +962,14 @@ if (is_android) {
     ]
   }
 
+  # Some android targets still depend on --gc-sections to link.
+  # TODO: remove --gc-sections for Debug builds (crbug.com/159847).
+  config("gc_sections") {
+    ldflags = [ "-Wl,--gc-sections" ]
+  }
+
   # GYP: //chrome/chrome_android.gypi:chrome_android_core
-  static_library("chrome_android_core") {
+  source_set("chrome_android_core") {
     sources = [
       "app/android/chrome_android_initializer.cc",
       "app/android/chrome_android_initializer.h",
@@ -974,6 +980,7 @@ if (is_android) {
       "app/chrome_main_delegate.cc",
       "app/chrome_main_delegate.h",
     ]
+    public_configs = [ ":gc_sections" ]
 
     include_dirs = [ android_ndk_include_dir ]