autoconf: use include directives instead of recursing down cmd

No installation diff, dist lost
  -zfs-2.1.99/cmd/fsck_zfs/fsck.zfs
which was distributed erroneously, since it's generated

Also clean gitrev on clean

Also add -e 'any possible bashisms' to default checkbashisms flags,
and fully parallelise it and shellcheck, and it works out-of-tree, too

Also align the Release in the dist META file correctly

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

etc/default/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 include $(top_srcdir)/config/Shellcheck.am
 
@@ -6,3 +8,4 @@ initconf_SCRIPTS = zfs
 SUBSTFILES += $(initconf_SCRIPTS)
 
 SHELLCHECK_SHELL = sh
+SHELLCHECKSCRIPTS += $(initconf_SCRIPTS)

etc/init.d/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 include $(top_srcdir)/config/Shellcheck.am
 
@@ -8,3 +10,4 @@ init_SCRIPTS = zfs-import zfs-load-key zfs-mount zfs-share zfs-zed
 SUBSTFILES += $(init_SCRIPTS)
 
 SHELLCHECK_SHELL = sh
+SHELLCHECKSCRIPTS += $(init_SCRIPTS)

etc/systemd/system/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 
 systemdpreset_DATA = \

etc/zfs/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 include $(top_srcdir)/config/Shellcheck.am
 
@@ -16,3 +18,4 @@ pkgsysconf_SCRIPTS = \
 SUBSTFILES += $(pkgsysconf_SCRIPTS)
 
 SHELLCHECK_SHELL = sh
+SHELLCHECKSCRIPTS += $(pkgsysconf_SCRIPTS)