Fix build-ui target to not damage .gitignore file
Fix build-ui target to not damage .gitignore file

Follow-up to #3698

Signed-off-by: Yuri Shkuro <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@ysh.us>

jaegertracing/jaeger,jaegertracing/jaeger,jaegertracing/jaeger,jaegertracing/jaeger,jaegertracing/jaeger