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/zdb/.gitignore

@@ -1 +0,0 @@
-/zdb

cmd/zdb/Makefile.am

@@ -1,18 +1,14 @@
-include $(top_srcdir)/config/Rules.am
+zdb_CPPFLAGS = $(AM_CPPFLAGS) $(FORCEDEBUG_CPPFLAGS)
 
-AM_CPPFLAGS += $(FORCEDEBUG_CPPFLAGS)
-
-sbin_PROGRAMS = zdb
+sbin_PROGRAMS   += zdb
+CPPCHECKTARGETS += zdb
 
 zdb_SOURCES = \
-	zdb.c \
-	zdb_il.c \
-	zdb.h
+	%D%/zdb.c \
+	%D%/zdb.h \
+	%D%/zdb_il.c
 
 zdb_LDADD = \
-	$(abs_top_builddir)/libzpool.la \
-	$(abs_top_builddir)/libzfs_core.la \
-	$(abs_top_builddir)/libnvpair.la
-
-include $(top_srcdir)/config/CppCheck.am
-CPPCHECKTARGETS += zdb
+	libzpool.la \
+	libzfs_core.la \
+	libnvpair.la