Script doesn't check for tool availability

filterdiff is used but not checked for. The instructions should probably at least advise to install the patchutils package that contains it.

$ make dist-srpm
make -C redhat dist-srpm 
make[1]: Entering directory '/home/hadess/Projects/kernel/kernel-ark/redhat'
BUILDID is ".test".
cd /home/hadess/Projects/kernel/kernel-ark/redhat/configs; rm -f kernel-*.config \
				kernel-*.config.orig \
				kernel-*.config.tmp
linux-20200721git4fa640dc5230.tar.xz unchanged...
cd /home/hadess/Projects/kernel/kernel-ark/redhat/configs; TARGET=fedora ./build_configs.sh kernel 
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-x86_64-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-x86_64-debug-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-ppc64le-rhel.config ... fatal: No names found, cannot describe anything.
Using 4fa640dc5230
Gathering new log entries since 4fa640dc5230
done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-ppc64le-debug-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-s390x-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-s390x-debug-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-s390x-zfcpdump-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-aarch64-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-aarch64-debug-rhel.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-x86_64-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-x86_64-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-i686-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-i686-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-ppc64le-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-ppc64le-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-s390x-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-s390x-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-aarch64-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-aarch64-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-armv7hl-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-armv7hl-debug-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-armv7hl-lpae-fedora.config ... done
Building /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-armv7hl-lpae-debug-fedora.config ... done
/bin/sh: /usr/bin/filterdiff: No such file or directory
cd /home/hadess/Projects/kernel/kernel-ark/redhat/configs; ./process_configs.sh -n -t -c kernel
Processing /home/hadess/Projects/kernel/kernel-ark/redhat/configs/kernel-aarch64-debug-fedora.config ... Found unset config items, please set them to an appropriate value
CONFIG_DRM_PANEL_XINGBANGDA_XBD599=n
make[1]: *** [Makefile:151: dist-configs-check] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory '/home/hadess/Projects/kernel/kernel-ark/redhat'
make: *** [makefile:12: dist-srpm] Error 2