Add the ability of unbundling JSC from weex_sdk.aar.

Author: YorkShen

android/build.gradle

@@ -76,6 +76,7 @@ ext {
     //Default value for disableCov is false
     disableCov = project.hasProperty("disableCov") && disableCov.equals("true")
     useApachePackageName = project.hasProperty('apachePackageName') ? project.property('apachePackageName').toBoolean() : false
+    unbundlingJSC = project.hasProperty('unbundlingJSC') ? project.property('unbundlingJSC').toBoolean() : false
     implementFromWeex = true
 }
 

android/sdk/build.gradle

@@ -209,6 +209,10 @@ android {
             main.java.srcDirs = ['src/legacyRelease/java']
             main.manifest.srcFile(new File('src/legacyRelease/AndroidManifest.xml'))
         }
+
+        if(project.unbundlingJSC){
+            main.jniLibs.srcDirs = []
+        }
     }
 
     compileOptions.encoding = "UTF-8"