fixing travis

.travis.yml

@@ -4,10 +4,6 @@ android:
     - platform-tools
     - tools
     - build-tools-23.0.2
-    - build-tools-23.0.1
-    - build-tools-23.0.0
-    - build-tools-22.0.1
-    - build-tools-21.1.2
     - build-tools-19.1.0
     - android-23
     - extra-android-m2repository

build.gradle

@@ -51,6 +51,12 @@ dependencies {
 	playstoreCompile 'com.google.android.gms:play-services-gcm:8.4.0'
 }
 
+ext {
+	travisBuild = System.getenv("TRAVIS") == "true"
+	// allows for -Dpre-dex=false to be set
+	preDexEnabled = "true".equals(System.getProperty("pre-dex", "true"))
+}
+
 android {
 	compileSdkVersion 23
 	buildToolsVersion "23.0.2"
@@ -64,6 +70,11 @@ android {
 		applicationId "eu.siacs.conversations"
 	}
 
+	dexOptions {
+		// Skip pre-dexing when running on Travis CI or when disabled via -Dpre-dex=false.
+		preDexLibraries = preDexEnabled && !travisBuild
+	}
+
 	compileOptions {
 		sourceCompatibility JavaVersion.VERSION_1_7
 		targetCompatibility JavaVersion.VERSION_1_7