Installation manifest doesn't respect prefix for `bash_completion.d/cargo`

[rillian]

Running the install script for the cargo package from channel-rust-nightly.toml I get an error:

install: creating uninstall script at /home/giles/firefox/taskcluster/docker/rust-build/rustc/lib/rustlib/uninstall.sh
install: installing component 'cargo'
install: cannot create regular file '/etc/bash_completion.d/cargo': Permission denied

It seems like installer isn't respecting the --prefix for the bash_completion file.

[rillian]

sysconfdir defaults to /etc without prepending the prefix. I'm not sure if that's helpful or not, but I suppose I can work around with DESTDIR or --sysconfdir=$prefix/etc

[alexcrichton]

cc @Keruspe, I think this changed recently in rust-lang/rust, right?

[Keruspe]

It changed in rust-installer indeed. Previously it would be unconditionally installed in $prefix/etc and it's now installed in $sysconfdir.
I hesitated between /etc and $prefix/etc for the default value and I actually followed what is done by rust configure script: https://github.com/rust-lang/rust/blob/master/configure#L469
Passing --sysconfdir would indeed fix your issue.

[Keruspe]

See rust-lang/rust-installer#64