Build with static libc++

Summary:
This avoids having to perform gymnastics like in
https://github.com/facebook/react-native/pull/26697

Reviewed By: jknoxville

Differential Revision: D17735954

fbshipit-source-id: 507548aab89309beeb228b104a24af8acd10ce9a

android/build.gradle

@@ -25,7 +25,7 @@ android {
 
         externalNativeBuild {
             cmake {
-                arguments '-DANDROID_TOOLCHAIN=clang', '-DANDROID_STL=c++_shared'
+                arguments '-DANDROID_TOOLCHAIN=clang', '-DANDROID_STL=c++_static'
                 targets 'flipper', 'event_shared', 'event_extra_shared', 'event_core_shared'
             }
         }

xplat/build.gradle

@@ -16,7 +16,7 @@ android {
         targetSdkVersion rootProject.targetSdkVersion
         externalNativeBuild {
             cmake {
-                arguments '-DANDROID_TOOLCHAIN=clang'
+                arguments '-DANDROID_TOOLCHAIN=clang', '-DANDROID_STL=c++_static'
             }
         }
     }