support CC=clang and LD=ld.lld

[phoepsilonix]

1. In the case of kernels built with clang/llvm and lld, clang/llvm and lld are also used to compile kernel modules.
2. Fixing typos ${make_command}

[scaronni]

Why another pull request for the same topic as in #169?

Also, as described in the above pull request, we're trying the approach of checking the .config file first.