Accept and fetch multiple packages

* Duplicated package names are skipped.
* A package name can be a simple base name like 'syn',
  or with version number like 'syn-1.0.5'.

Test: get_rust_pkg.py -h
Test: get_rust_pkg.py pkg1 pkg2 pkg3
Test: get_rust_pkg.py -o tmp -v pkg1 pkg2 pkg1
Change-Id: I5757f20c9a7cb244dc4b06113e28fcf4585c0703
1 file changed