Comment 1 for bug 1218209

Due to https://bugs.launchpad.net/ubuntu/+source/lcov/+bug/1163758 it looks like lcov is currently incompatible with newer versions of GCC, so I'll just yank the build-dep from llvm-toolchain instead, and we can revisit this if someone wants to rev lcov to a newer version and include the patches from upstream CVS to fix it.