[Cronet] Use gn desc to find third party licenses on Android.

components/cronet/android/BUILD.gn

Index: components/cronet/android/BUILD.gn
diff --git a/components/cronet/android/BUILD.gn b/components/cronet/android/BUILD.gn
index 9abfac79468f67f4c1e96afba08e98da33843615..24e769521ce689fd428645de0c416bac1cc96c03 100644
--- a/components/cronet/android/BUILD.gn
+++ b/components/cronet/android/BUILD.gn
@@ -1203,12 +1203,19 @@ action("generate_licenses") {
   _license_path = "$_package_dir/LICENSE"
 
   script = "//components/cronet/tools/cronet_licenses.py"
+  inputs = [
+    "//build/util/LASTCHANGE",
+    "//buildtools/linux64/gn",
+  ]
   outputs = [
     _license_path,
   ]
   args = [
     "license",
     rebase_path(_license_path, root_build_dir),
+    "--gn",
+    "--gn-path",
+    rebase_path("//buildtools/linux64/gn", root_build_dir),
   ]
 }