This allows (cross-)building gdb-minimal for the Hurd.
* gnu/packages/patches/gdb-fix-gnu-nat-build.patch: New file, taken from
upstream.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/web.scm (gdb)[inputs]: When building for the Hurd, add it.
[arguments]: When building for the Hurd, apply it.