gnu: glibc: Add "static" output.

gnu: glibc: Add "static" output.

This shrinks glibc:out from 37 MiB to 29 MiB.

* gnu/packages/base.scm (glibc/linux)[outputs]: Add "static".
[arguments]: Add #:modules.  Add 'move-static-libs' phase.
* gnu/packages/commencement.scm (static-bash-for-glibc): Augment
 #:configure-flags to pass "-L LIBC:STATIC".  Add the "static" output of
GLIBC-FINAL to 'inputs'.
(%boot2-inputs, %final-inputs): Likewise.
(canonical-package): Adjust to deal with multiple-output packages.
* gnu/packages/cross-base.scm (cross-gcc): Add the "static" output of
LIBC to 'native-inputs'.