Fix build with system harfbuzz

build/linux/unbundle/harfbuzz-ng.gn

Index: build/linux/unbundle/harfbuzz-ng.gn
diff --git a/build/linux/unbundle/harfbuzz-ng.gn b/build/linux/unbundle/harfbuzz-ng.gn
index 971ccab284f9fcec06d50cd373dfc14157b27437..5c422db1034332dfef06d93ad12ad6db51c64853 100644
--- a/build/linux/unbundle/harfbuzz-ng.gn
+++ b/build/linux/unbundle/harfbuzz-ng.gn
@@ -17,7 +17,21 @@ shim_headers("harfbuzz_shim") {
   headers = [ "hb.h" ]
 }
 
-source_set("harfbuzz-ng") {
+group("harfbuzz-ng") {
+  public_deps = [
+    ":harfbuzz-ng-ft",
+    ":harfbuzz-ng-without-freetype",
+  ]
+}
+
+source_set("harfbuzz-ng-ft") {
+  deps = [
+    ":harfbuzz_shim",
+  ]
+  public_configs = [ ":system_harfbuzz" ]
+}
+
+source_set("harfbuzz-ng-without-freetype") {
   deps = [
     ":harfbuzz_shim",
   ]