Fixed dependencies on 'repo' and corrected import URLs

Removed dependencies on (now removed) `repo` package and updated import paths. This was causing `src toolchain install-std` to fail.

Some still fail with a large amount of messages of the like:
```
	stdlib_test.go:89: def {pkg:syscall path:Listxattr/_p1} /usr/local/go/src/syscall/zsyscall_linux_ppc64.go:16052-16055 already defined at /usr/local/go/src/syscall/zsyscall_linux_ppc64le.go:16052-16055
	stdlib_test.go:89: def {pkg:syscall path:Kill/sig} /usr/local/go/src/syscall/zsyscall_linux_ppc64le.go:14914-14917 already defined at /usr/local/go/src/syscall/zsyscall_linux_ppc64.go:14914-14917
```