* gnu/packages/patches/libxcrypt-hurd64.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/crypto.scm (libxcrypt)[arguments]: When building for the 64bit
Hurd, use it in new phase `apply-hurd64-patch'.
Change-Id: I795a591ef8282ee5b760fec43bd4ad849007f602