Add convenience target clean-junk

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
Merge pull request #359 from TimothyGu/temp-rem

Add convenience target clean-junk
s3-fetch-and-sync: use clean-junk instead of clean-pkg
package libarchive: enable shared build
package liboauth: enable shared build
update package vmime
update package vmime