Installer tries create directory outside DESTDIR

[yshui]

rust/src/bootstrap/install.rs

Lines 76 to 81 in 2ad5292

	let prefix = builder.config.prefix.as_ref().map_or(prefix_default, |p| {
	fs::create_dir_all(p)
	.unwrap_or_else(|err| panic!("could not create {}: {}", p.display(), err));
	fs::canonicalize(p)
	.unwrap_or_else(|err| panic!("could not canonicalize {}: {}", p.display(), err))
	});

This creates the prefix directory without DESTDIR prepended.