* distro/ld-wrapper.scm: New file.
* Makefile.am (MODULES): Add it.
* distro/base.scm (ld-wrapper-boot3): New variable.
(%boot3-inputs): Add LD-WRAPPER-BOOT3.
(bash-final, guile-final, ld-wrapper): New final.
(%final-inputs): Use BASH-FINAL; add LD-WRAPPER.
(gcc-4.7): Remove the `-rpath' trick from the `lib' spec string.