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Since abuild v2.22.0, these are removed automatically unless 'libtool'
option has been specified.

upstream report:
https://github.com/FreeRADIUS/freeradius-server/issues/1222

Also add install_if on existing bash-completion subpackage

fixes #4613

Also install go and gofmt binary to /usr/lib/go/bin and symlink it to
/usr/bin. Also fix removal of tests.

To avoid that $GOROOT_BOOTSTRAP equals $GOROOT during main/go build.

See:
- https://github.com/golang/go/commit/f9379eb3467d2b6feb8fb0c7c2c366b81408305d

Also: Cleanup package further and fix removal of _test.go packages.