[backport] Add buildcharacter.properties to .gitignore.
[backport] Add buildcharacter.properties to .gitignore.

(cherry picked from commit 693e55e1cb75055bb243ffca2e18b8e44e80bb8c)

shimib/scala,shimib/scala,lrytz/scala,scala/scala,slothspot/scala,slothspot/scala,slothspot/scala,jvican/scala,scala/scala,scala/scala,felixmulder/scala,scala/scala,lrytz/scala,martijnhoekstra/scala,shimib/scala,martijnhoekstra/scala,lrytz/scala,slothspot/scala,felixmulder/scala,slothspot/scala,jvican/scala,felixmulder/scala,felixmulder/scala,felixmulder/scala,jvican/scala,lrytz/scala,lrytz/scala,martijnhoekstra/scala,scala/scala,jvican/scala,shimib/scala,jvican/scala,felixmulder/scala,slothspot/scala,martijnhoekstra/scala,jvican/scala,lrytz/scala,slothspot/scala,martijnhoekstra/scala,scala/scala,shimib/scala,martijnhoekstra/scala,shimib/scala,felixmulder/scala,jvican/scala