debian: Do not build for riscv64

The build requirements could not be satisfied
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

debian/build.sh

@@ -2,7 +2,7 @@
 
 set -x
 
-ARCHITECTURES=( amd64 arm64 i386 armhf riscv64 )
+ARCHITECTURES=( amd64 arm64 i386 armhf )
 RELEASES=( buster )
 
 CHROOT_PATH="/var/tmp"