Remove extra ';'

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185247 91177308-0d34-0410-b5e6-96231b3b80d8
Move a function into assert() so that GCC won't complain that the
function is not used in release build.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185248 91177308-0d34-0410-b5e6-96231b3b80d8