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/zhack/.gitignore

@@ -1 +0,0 @@
-/zhack

cmd/zhack/Makefile.am

@@ -1,16 +1,12 @@
-include $(top_srcdir)/config/Rules.am
+zhack_CPPFLAGS = $(AM_CPPFLAGS) $(FORCEDEBUG_CPPFLAGS)
 
-AM_CPPFLAGS += $(FORCEDEBUG_CPPFLAGS)
-
-sbin_PROGRAMS = zhack
+sbin_PROGRAMS   += zhack
+CPPCHECKTARGETS += zhack
 
 zhack_SOURCES = \
-	zhack.c
+	%D%/zhack.c
 
 zhack_LDADD = \
-	$(abs_top_builddir)/libzpool.la \
-	$(abs_top_builddir)/libzfs_core.la \
-	$(abs_top_builddir)/libnvpair.la
-
-include $(top_srcdir)/config/CppCheck.am
-CPPCHECKTARGETS += zhack
+	libzpool.la \
+	libzfs_core.la \
+	libnvpair.la