Template: Specify abiFilters if enableSeparateBuildPerCPUArchitecture is not set.

Summary:
As users can toggle `enableSeparateBuildPerCPUArchitecture` to create a split APK, once that is off, the `-PreactNativeArchitecture` is not correctly considered when building the local module.

This will make sure that, if users have `enableSeparateBuildPerCPUArchitecture` set to `false`, their
app is building the local `app_modules` only for the requested architectures.

Practically, users invoking with `--active-arch-only` might experience a build failure if they have a fully clean environment (would be forced to do a full build before using `--active-arch-only`). This addresses this scenario.

Changelog:
[Android] [Fixed] - Template: Specify abiFilters if enableSeparateBuildPerCPUArchitecture is not set.

Reviewed By: ShikaSD

Differential Revision: D35250700

fbshipit-source-id: 4e555888636cf182495fab2b4a562d93a70b9e66

Author: cortinico

template/android/app/build.gradle

@@ -159,6 +159,11 @@ android {
                     targets "helloworld_appmodules"
                 }
             }
+            if (!enableSeparateBuildPerCPUArchitecture) {
+                ndk {
+                    abiFilters (*reactNativeArchitectures())
+                }
+            }
         }
     }