Fixes other targets rustlibs installation
Fixes other targets rustlibs installation

When the user select more than one target to generate rustlibs for, rustbuild will only install the host one.

This patch fixes it, more info in https://github.com/rust-lang/rust/issues/39235#issuecomment-285878858

GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust