Centralize variable substitution

A bunch of places need to edit files to incorporate the configured paths
i.e. bindir, sbindir etc. Move this logic into a common file.

Create arc_summary by copying arc_summary[23] as appropriate at build
time instead of install time.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes #10559

cmd/arc_summary/.gitignore

@@ -0,0 +1 @@
+arc_summary

cmd/arc_summary/Makefile.am

@@ -1,4 +1,7 @@
-transform = $(program_transform_name)
+bin_SCRIPTS = arc_summary
+
+CLEANFILES = arc_summary
+EXTRA_DIST = arc_summary2 arc_summary3
 
 if USING_PYTHON_2
 SCRIPT = arc_summary2
@@ -6,9 +9,5 @@ else
 SCRIPT = arc_summary3
 endif
 
-dist_bin_SCRIPTS = $(SCRIPT)
-
-install-exec-hook:
-	before=$$(echo $(SCRIPT) | sed '$(transform)'); \
-	after=$$(echo arc_summary | sed '$(transform)'); \
-	mv "$(DESTDIR)$(bindir)/$$before" "$(DESTDIR)$(bindir)/$$after"
+arc_summary: $(SCRIPT)
+	cp $< $@

cmd/arcstat/.gitignore

@@ -0,0 +1 @@
+arcstat

cmd/arcstat/Makefile.am

@@ -1,13 +1,5 @@
-dist_bin_SCRIPTS = arcstat
+include $(top_srcdir)/config/Substfiles.am
 
-#
-# The arcstat script is compatible with both Python 2.6 and 3.4.
-# As such the python 3 shebang can be replaced at install time when
-# targeting a python 2 system.  This allows us to maintain a single
-# version of the source.
-#
-if USING_PYTHON_2
-install-exec-hook:
-	$(SED) ${ac_inplace} -e 's|^#!/usr/bin/env python3|#!/usr/bin/env python2|' \
-	    $(DESTDIR)$(bindir)/arcstat
-endif
+bin_SCRIPTS = arcstat
+
+SUBSTFILES += $(bin_SCRIPTS)

cmd/arcstat/arcstat.in

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env @PYTHON_SHEBANG@
 #
 # Print out ZFS ARC Statistics exported via kstat(1)
 # For a definition of fields, or usage, use arcstat -v

cmd/dbufstat/.gitignore

@@ -0,0 +1 @@
+dbufstat

cmd/dbufstat/Makefile.am

@@ -1,13 +1,5 @@
-dist_bin_SCRIPTS = dbufstat
+include $(top_srcdir)/config/Substfiles.am
 
-#
-# The dbufstat script is compatible with both Python 2.6 and 3.4.
-# As such the python 3 shebang can be replaced at install time when
-# targeting a python 2 system.  This allows us to maintain a single
-# version of the source.
-#
-if USING_PYTHON_2
-install-exec-hook:
-	$(SED) ${ac_inplace} -e 's|^#!/usr/bin/env python3|#!/usr/bin/env python2|' \
-	    $(DESTDIR)$(bindir)/dbufstat
-endif
+bin_SCRIPTS = dbufstat
+
+SUBSTFILES += $(bin_SCRIPTS)

cmd/dbufstat/dbufstat.in

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env @PYTHON_SHEBANG@
 #
 # Print out statistics for all cached dmu buffers.  This information
 # is available through the dbufs kstat and may be post-processed as

cmd/zed/zed.d/Makefile.am

@@ -1,8 +1,7 @@
 include $(top_srcdir)/config/Rules.am
+include $(top_srcdir)/config/Substfiles.am
 
-EXTRA_DIST = \
-	README \
-	history_event-zfs-list-cacher.sh.in
+EXTRA_DIST += README
 
 zedconfdir = $(sysconfdir)/zfs/zed.d
 
@@ -29,12 +28,7 @@ dist_zedexec_SCRIPTS = \
 
 nodist_zedexec_SCRIPTS = history_event-zfs-list-cacher.sh
 
-$(nodist_zedexec_SCRIPTS): %: %.in
-	-$(SED) -e 's,@bindir\@,$(bindir),g' \
-		-e 's,@runstatedir\@,$(runstatedir),g' \
-		-e 's,@sbindir\@,$(sbindir),g' \
-		-e 's,@sysconfdir\@,$(sysconfdir),g' \
-		$< >'$@'
+SUBSTFILES += $(nodist_zedexec_SCRIPTS)
 
 zedconfdefaults = \
 	all-syslog.sh \