Fixes a Coveralls issue
Fixes a Coveralls issue

Coveralls failed because it couldn't access the gcov files within the
build directory. The --exclude parameter was forbidding coveralls to
access the 'build' directory, which has proven to be too restrictive.

http2d/core,alobbs/libhpack,alobbs/libhpack,http2d/core,http2d/core,alobbs/libhpack,alobbs/libhpack,http2d/core