This PR brings back limited debuginfo which allows for nice backtraces and breakpoints, but omits any info about variables and types.
The `-g` and `--debuginfo` command line options have been extended to take an optional argument:
`-g0` means no debug info.
`-g1` means line-tables only.
`-g2` means full debug info.
Specifying `-g` without argument is equivalent to `-g2`.
Fixes #12280