Require Build Tools 19.0.3.
Release apk signed with debug key if no keystore

You have to edit a gradle.properties file with the following structure:
storeFileProperty=fullPath
storePasswordProperty=store password without quotation marks
keyAliasProperty=key alias without quotation marks
keyPasswordProperty=key password without quotation marks
Build tools and gradle.properties explanation
Merge branch 'bug/adjust-build-tools-version-#5491' into develop