fix androidX legacy dependencies...

this is a hacky way to detect when to use the legacy dependecies
from androidX.

android/build.gradle

@@ -46,7 +46,19 @@ dependencies {
 
     compileOnly "com.facebook.react:react-native:+"
     implementation "com.google.android.libraries.places:places:1.1.0"
-    implementation "com.android.support:appcompat-v7:${supportLibVersion}"
-    implementation "com.android.support:support-v4:${supportLibVersion}"
     implementation "com.google.code.findbugs:jsr305:3.0.2"
+
+    Properties prop = new Properties();
+    InputStream input = null;
+
+    input = new FileInputStream("gradle.properties");
+    prop.load(input);
+
+    if (prop.getProperty("android.useAndroidX")) {
+        implementation "androidx.appcompat:appcompat:1.0.2"
+        implementation "androidx.legacy:legacy-support-v4:1.0.0"
+    } else {
+        implementation "com.android.support:appcompat-v7:${supportLibVersion}"
+        implementation "com.android.support:support-v4:${supportLibVersion}"
+    }
 }