Bug 1238788 - Burn the tree on android lint failure. r=nalexander

Looking at [1], we halt_on_failure for the `postflight_build_mach_command`s and
the flag I flipped causes the lint command to return a non-zero exit code (i.e.
noting failure).

[1]: https://hg.mozilla.org/mozilla-central/rev/b7f1dac8306f#l2.29

MozReview-Commit-ID: 8v4am9zxxCk

mobile/android/app/build.gradle

@@ -31,7 +31,7 @@ android {
     }
 
     lintOptions {
-        abortOnError false
+        abortOnError true
     }
 
     buildTypes {