Add -clc command line option to point to a different compiler

Ghost User
2019-10-31T14:08:16+01:00

This allows using the `-clc` command line option to point to a different compiler than the default `cocl`/`CleanCompiler.exe`. This is useful now that the nightly builds include both `cocl` and `cocl-itasks`, so that you can use `clm -clc cocl-itasks ...`.