rust-overlay: nightly 2017-05-19 tries to write to /etc

[Ralith]

The build fails with mkdir: cannot create directory '/etc/bash_completion.d': Permission denied

[steveej]

We have two options here:

• remove them from the source before installing
• install them to $out/share/bash-completion/completions

[zimbatm]

(2) is the right answer. Upstream should be fixed to respect the destdir on install. They will want to support that on normal Linuxes as well.

[nbp]

This issue seem to be coming from rust-lang/rust-installer#59
I guess the problem seems to be that --prefix is not considered for the default value of --sysconfigdir, in the mean time I guess we could provided it as argument of the install script.

[nbp]

And is a duplicate of rust-lang/rust#42102 fixed by rust-lang/rust#42124