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

cmd/zfs/.gitignore

@@ -1 +0,0 @@
-/zfs

cmd/zfs/Makefile.am

@@ -1,26 +1,22 @@
-include $(top_srcdir)/config/Rules.am
-
-sbin_PROGRAMS = zfs
+sbin_PROGRAMS   += zfs
+CPPCHECKTARGETS += zfs
 
 zfs_SOURCES = \
-	zfs_iter.c \
-	zfs_iter.h \
-	zfs_main.c \
-	zfs_util.h \
-	zfs_project.c \
-	zfs_projectutil.h
+	%D%/zfs_iter.c \
+	%D%/zfs_iter.h \
+	%D%/zfs_main.c \
+	%D%/zfs_project.c \
+	%D%/zfs_projectutil.h \
+	%D%/zfs_util.h
 
 zfs_LDADD = \
-	$(abs_top_builddir)/libzfs.la \
-	$(abs_top_builddir)/libzfs_core.la \
-	$(abs_top_builddir)/libnvpair.la \
-	$(abs_top_builddir)/libuutil.la
+	libzfs.la \
+	libzfs_core.la \
+	libnvpair.la \
+	libuutil.la
 
 zfs_LDADD += $(LTLIBINTL)
 
 if BUILD_FREEBSD
 zfs_LDADD += -lgeom -ljail
 endif
-
-include $(top_srcdir)/config/CppCheck.am
-CPPCHECKTARGETS += zfs