I think this is confusing Homebrew.

Install to directories instead of filenames. We don't need the
filenames, and on top of that, `$(MAN_PAGE)` was wrong, as it includes
the "doc/" prefix.

I'm getting a destroot error in MacPorts:

    Failed to activate wajir: Image error: /bin already exists and does
    not belong to a registered port.

Trying to see if this fixes it.

Create the man page directory before installing it. Otherwise it fails
to install.

Also use 644 permissions on the man page as that's more appropriate.

`DESTDIR` seems to be more standardised.

Didn't set the variable because according to the Make manual, you're not
supposed to:

> You should not set the value of DESTDIR in your Makefile at all

https://www.gnu.org/software/make/manual/make.html#DESTDIR_003a-Support-for-Staged-Installs

Put all files in the tarball in a `wajir_$(VERSION)` folder. Otherwise,
MacPorts couldn't figure out where the root directory was.

This seemed to cause the `bundle` target to be run even in the packaged
release tarball. In that case, the 'bundle/' directory should already
exist, and we don't want to rebuild it.

We might also have been able to resolve this by generating the 'bundle/'
tar before the project `git archive` tar, but I couldn't figure out how
to concatenate two tars together with BSD tar.

Packages source files including dependencies for release.