fix compilation two issues

[1a1a11a]

1. remove cmake from Ubuntu apt installation because the cmake installed from apt (both Ubuntu18 and Ubuntu20) is too old to be used, and the new cmake from apt shadows existing cmake binary.
2. current compilation cannot use multiple cores even though -j is specified due to a bug in using nproc.

[therealgymmy]

if we remove cmake from dependency, do we expect users to have installed cmake from a newer source?

[wonglkd]

FYI @1a1a11a , re cmake being too old: I'm not sure if your cmake issue was the same as mine, but I did face a compilation issue on Ubuntu20 due to zstd 1.5.4 (https://github.com/facebook/zstd/issues/3500) using a feature only present in cmake >= 3.18. It seems like they have resolved this issue upstream by eliminating the use of that feature, with the fix committed and expected in the next release.

(For myself, I resolved my issue by going back to Ubuntu18.)

[1a1a11a]

Oh, this is helpful! In that case, then we can keep cmake

[1a1a11a]

updated