Honoring DT_RUNPATH in cross-ld

[Ludovic Courtès]

By default, cross ld does not honor DT_RPATH/DT_RUNPATH entries when
searching for a NEEDed shared library.

This behavior can be changed by configuring --with-sysroot, because
genscripts.sh sets USE_LIBPATH=yes as a side effect, which in turn
enables RUNPATH search in elf32.em.

Sometimes this lookup rule is needed even though the system has nothing
like a sysroot (this is the case with GNU Guix, which installs each
package in its own directory, à la Stow.)

What about providing a separate configure option specifically for this?

Thanks,
Ludo’.