Android Studio integration

[kkaefer]

Once we have #5359 in, we can start adding Android Studio support. Starting in 2.2, they support externalNativeBuild and have explicit integration for CMake.

Here's a preliminary patch:

diff --git a/platform/android/MapboxGLAndroidSDK/build.gradle b/platform/android/MapboxGLAndroidSDK/build.gradle
index 38688a9..84b4a69 100644
--- a/platform/android/MapboxGLAndroidSDK/build.gradle
+++ b/platform/android/MapboxGLAndroidSDK/build.gradle
@@ -33,9 +33,20 @@ android {
     compileSdkVersion Integer.parseInt(project.ANDROID_BUILD_SDK_VERSION)
     buildToolsVersion project.ANDROID_BUILD_TOOLS_VERSION

+    externalNativeBuild {
+        cmake {
+            path "../../../CMakeLists.txt"
+        }
+    }
     defaultConfig {
         minSdkVersion Integer.parseInt(project.ANDROID_MIN_SDK)
         targetSdkVersion Integer.parseInt(project.ANDROID_BUILD_TARGET_SDK_VERSION)
+        externalNativeBuild {
+            cmake {
+                arguments "-DANDROID_TOOLCHAIN=clang"
+                arguments "-DMBGL_PLATFORM=android"
+            }
+        }
     }

     sourceSets {
diff --git a/platform/android/build.gradle b/platform/android/build.gradle
index 4225752..fa9f871 100644
--- a/platform/android/build.gradle
+++ b/platform/android/build.gradle
@@ -6,7 +6,7 @@ buildscript {
         maven { url 'https://jitpack.io' }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.1.2'
+        classpath 'com.android.tools.build:gradle:2.2.0-alpha6'
         classpath 'com.github.JakeWharton:sdk-manager-plugin:220bf7a88a7072df3ed16dc8466fb144f2817070'

         // NOTE: Do not place your application dependencies here; they belong

Unfortunately, the android.toolchain.cmake file they ship with does not contain support for using the libc++ STL, which we require. Ticket is at https://code.google.com/p/android/issues/detail?id=212931

[jfirebaugh]

Landed in #8363.