fix: use --force when running npm pack

This flag should fix a race condition we are seeing according to the
error message:

```
npm ERR! Could not move /tmp/npm-106-07447faf/tmp/packing-989d668d/bitgo-common-1.0.0.tgz to bitgo-common-1.0.0.tgz: destination already exists.
npm ERR! File exists: undefined
npm ERR! Remove the existing file and try again, or run npm
npm ERR! with --force to overwrite files recklessly.
```

Author: bitgopatmcl

templates/makefile

@@ -28,7 +28,7 @@ $({{ unscoped_package_name.replace("-", "_").to_uppercase() }}_INTERNAL_DEPENDEN
 # re-compile its input sources. Since we don't have the list of sources available here,
 # let's invoke pack only when the file does not exist.
 {{ pack_archive_filename }}:
-	cd {{ package_directory }}; npm pack
+	cd {{ package_directory }}; npm pack --force
 
 {{ unscoped_package_name.replace("-", "_").to_uppercase() }}_INTERNAL_NPM_DEPENDENCIES_EXCLUSIVE = {{ internal_npm_dependencies_exclusive.join(" \\\n") }}