fix(make-depends): do not delete npm pack archive

Since `mv` "deletes" the source file on disk, we have a race condition
where two actors are trying to build the same tarball.

Consider two tasks, t_a and t_b. The optimal happy path looks like

1. t_a runs `npm pack`, creating the tarball in the package dir 2. t_a
runs `mv` to move the tarball into `/dist` 3. t_b sees the tarball in
`/dist` and takes no action

A less happy path can occur, due to the length of time `npm pack`
can take (~1s)

1. t_a runs `npm pack`, creating the tarball in the package dir
2. t_b runs `npm pack`, creating the tarball in the package dir
3. t_a runs `mv` to move the tarball into `/dist`
4. t_b runs `mv` to move the tarball into `/dist` <-- error!

Step 4 here will fail with an error like

```
mv: can't rename 'packages/my-package/scoped-my-package-1.2.3.tgz':
No such file or directory
```

because the first `mv` removes the tarball from disk.

This brings into question the sanity of using a top-level `/dist`
in the first place!  Ideally we'd atomically write the tarball into
`/dist` with npm 7's pack-destination[^1], but this flag is not
present in npm 6.

TODO: remove the `/dist` convention all-together

[^1]: https://docs.npmjs.com/cli/v7/commands/npm-pack#pack-destination

Author: EricCrosson

templates/makefile

@@ -27,7 +27,7 @@ $({{ unscoped_package_name.replace("-", "_").to_uppercase() }}_INTERNAL_DEPENDEN
 # NOTE: when npm 7+ supports a pack-destination so when npm 6 is EOL we should migrate to that
 dist/{{ scoped_package_name.trim_start_matches("@").replace("/", "-") }}.tgz: | dist
 	cd {{ package_directory }}; npm pack
-	mv {{ package_directory }}/{{ scoped_package_name.trim_start_matches("@").replace("/", "-") }}-$({{ unscoped_package_name.replace("-", "_").to_uppercase() }}_VERSION).tgz $@
+	ln {{ package_directory }}/{{ scoped_package_name.trim_start_matches("@").replace("/", "-") }}-$({{ unscoped_package_name.replace("-", "_").to_uppercase() }}_VERSION).tgz $@
 
 {{ unscoped_package_name.replace("-", "_").to_uppercase() }}_INTERNAL_NPM_DEPENDENCIES = {{ exclusive_transitive_internal_dependency_npm_pack_archives.join(" \\\n") }}