Add archiver to reference tables

[awvwgk]

Meson allows to set the archiver via the AR environment variable and a native / cross file. Only the latter approach seems to be documented. This patch adds the AR environment variable to the reference tables next to the compilers.

[eli-schwartz]

I've taken the liberty to reformat your commit message. git commit messages should not be one line per paragraph, but rather one block of lines per paragraph -- same rules as markdown. This makes it more readable in various contexts, though github will still reflow it using markdown rules when generating the default description for a PR.