hurd-amd64: also drop arch-specific rules supported by generic rules

[Samuel Thibault <sthibault@debian.org>]

Hello,

patch_glibc has a patch to move all headers to multiarch locations,
which drops the hurd-i386-specific rules, it should also drop the
hurd-amd64-specific rules, as the attached patch does, also available in
my tree

git@salsa.debian.org:sthibault/rebootstrap.git

as 61bbb54c44848a20d1a696bdc3ab1b0dbb07b694

Samuel

commit 61bbb54c44848a20d1a696bdc3ab1b0dbb07b694
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Sun Jul 14 13:00:13 2024 +0200

    Drop hurd-amd64-specific rules to move headers to multiarch directory
    
    Like for hurd-i386 above, this is already covered by the generic rules.

diff --git a/bootstrap.sh b/bootstrap.sh
index 1adf9d2..3aeca23 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -2509,6 +2509,14 @@ EOF
  endef
  
  # FIXME: We are having runtime issues with ifunc...
+--- a/debian/sysdeps/hurd-amd64.mk
++++ b/debian/sysdeps/hurd-amd64.mk
+@@ -18,5 +18,2 @@ endif
+ define libc_extra_install
+-mkdir -p $(debian-tmp)/usr/include/$(DEB_HOST_MULTIARCH)/mach
+-mv $(debian-tmp)/usr/include/mach/x86_64 $(debian-tmp)/usr/include/$(DEB_HOST_MULTIARCH)/mach/
+-ln -s ../$(DEB_HOST_MULTIARCH)/mach/x86_64 $(debian-tmp)/usr/include/mach/x86_64       
+ endef
 EOF
 }
 buildenv_glibc() {