Android: Fix incremental_install=true gn gen failure for arm64

Bug: 1013688
Change-Id: Iff04a8d0c4b4fdf8f143bd0a66a6f46cf0dc447d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879900
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709614}

build/config/android/rules.gni

@@ -3234,7 +3234,7 @@ if (enable_java_templates) {
         if (_proguard_enabled) {
           args += [ "--show-proguard-warning" ]
         }
-        if (_native_libs_deps != []) {
+        if (defined(_native_libs_file_arg)) {
           args += [ "--native-libs=$_native_libs_file_arg" ]
           deps += [ _native_libs_file_arg_dep ]
         }