Makefile: zfs-tests lives in srcdir; zfs-tests: accept common.sh path

This fixes out-of-tree builds

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13316

Makefile.am

@@ -75,8 +75,7 @@ distclean-local::
 		-type f -delete
 
 all-local:
-	-[ -x ${top_builddir}/scripts/zfs-tests.sh ] && \
-	    ${top_builddir}/scripts/zfs-tests.sh -c
+	-SCRIPT_COMMON=$(top_builddir)/scripts/common.sh $(top_srcdir)/scripts/zfs-tests.sh -c
 
 dist-hook:
 	$(AM_V_GEN)$(top_srcdir)/scripts/make_gitrev.sh -D $(distdir) $(GITREV)

scripts/zfs-tests.sh

@@ -26,13 +26,8 @@
 # Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
 #
 
-BASE_DIR=$(dirname "$0")
-SCRIPT_COMMON=common.sh
-if [ -f "${BASE_DIR}/${SCRIPT_COMMON}" ]; then
-	. "${BASE_DIR}/${SCRIPT_COMMON}"
-else
-	echo "Missing helper script ${SCRIPT_COMMON}" && exit 1
-fi
+SCRIPT_COMMON=${SCRIPT_COMMON:-${0%/*}/common.sh}
+. "${SCRIPT_COMMON}" || exit
 
 PROG=zfs-tests.sh
 VERBOSE="no"