Move to build tools 24.0.1 for support library.

Bug: None
Test: gradlew assemble assembleAndroidTest still compiles
Change-Id: I3597bc8333e4aa4f6a97f8b3ba9a45c6f5dcd566
diff --git a/build.gradle b/build.gradle
index e47de23..7236469 100644
--- a/build.gradle
+++ b/build.gradle
@@ -34,7 +34,7 @@
 ext.supportVersion = '25.1.0-SNAPSHOT'
 ext.extraVersion = 40
 ext.supportRepoOut = ''
-ext.buildToolsVersion = '23.0.2'
+ext.buildToolsVersion = '24.0.1'
 ext.buildNumber = Integer.toString(ext.extraVersion)
 
 ext.testRunnerVersion = '0.6-alpha'