* gnu/packages/gdb.scm (gdb-9.1)[native-inputs]: When compiling for the Hurd,
add required build dependency mig.
["arguments"]: Add "binutils" fall-back lookup in native-inputs for
cross-builds.
* gnu/packages/patches/gdb-hurd.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gdb.scm (gdb-9.2): Use it.
