Previous "test -x opt/gnu/bin/guile" would fail if the store item
"opt/gnu/bin" points to had been GC'd.
* tests/guix-pack.sh: Replace "test -x" with "test -L" to deal with
store items that have been reclaimed.
* guix/scripts/pack.scm (bootstrap-xz): New variable.
(%options) <--bootstrap>: New option.
(show-help): Document the new --bootstrap option.
(guix-pack): When --bootstrap is specified, use the bootstrap Guile,
tar, and xz to build the pack, and do not use any profile hooks or
locales.
* doc/guix.texi (Invoking guix pull): Document the new --bootstrap
option.
* tests/guix-pack.sh: New file.
* Makefile.am (SH_TESTS): Add guix-pack.sh.
* gnu/packages/package-management.scm (guix) <inputs>: Add util-linux.
