Reorganize native dep download and extraction (#154)

Summary:
This moves the native setup to a separate gradle file and unpacks everything outside the build folder. That way we don't throw everything away on every incremental build.

This is an intermediate step to get to a more declarative setup like Fresco has it and get rid of the individual hacks we have for every download.
Pull Request resolved: https://github.com/facebook/Sonar/pull/154

Reviewed By: jknoxville

Differential Revision: D8833812

Pulled By: passy

fbshipit-source-id: 2424c9d6e22e6092c04af344e06939b4a6aba041

android/third-party/build.gradle

@@ -0,0 +1,24 @@
+apply plugin: 'com.android.library'
+apply from: 'native.gradle'
+
+android {
+    compileSdkVersion rootProject.compileSdkVersion
+    buildToolsVersion rootProject.buildToolsVersion
+
+    defaultConfig {
+        minSdkVersion rootProject.minSdkVersion
+        targetSdkVersion rootProject.targetSdkVersion
+    }
+
+    sourceSets {
+        main {
+            manifest.srcFile './AndroidManifest.xml'
+        }
+    }
+}
+
+task prepare(dependsOn: [prepareAllLibs]) {
+}
+
+build.dependsOn prepare
+clean.dependsOn cleanNative