Update tar syntax to support OpenBSD.

[opsbob]

This PR special-cases the archive extraction code when executed on OpenBSD. This is to workaround the use of the -J and --strip-components options, which OpenBSD's tar does not support. If the xz format archive was downloaded, it correctly calls xzcat and pipes the output to tar. If not, it correctly calls the tar with the normal compression flag. In either case, it does not append the --strip-components=1 option, but rather uses the -s option to perform ed(1)-style basic regex replacement on the path.

This is tested to execute correctly on OpenBSD 7.0 (current release as of this PR). It does not address compilation issues of the downloaded node source code, as mentioned in #2134, which will likely require upstreaming of some subset of the OpenBSD-specific source patches that were developed for the OpenBSD ports build of node (see the OpenBSD patches for node-12.22.7 here or the implementation of binary builds for OpenBSD, but it does allow you to reach that step without error. This should, however, fully address #2660.

Fixes #2660.

[ljharb]

Thanks!

[ljharb]

This looks great! You'll also need to add nvm_extract_tarball to the nvm unload list. It'd also be ideal to add a unit test for this function - even if all it does is check that it requires 4 arguments (altho a step up from that would be overriding the PATH to point to a faked tar/gtar/xzcat and actually test that the right thing is invoked in each scenario)