Fix parallel make srpm

When building srpm using make -j, each of the recursive makes invoked to
build srpm-{dkms,kmod,utils} will build the dist target. This is both
unnecessary, and also has a very good chance of breaking when they race
trying to build gitrev.

Fix this by make dist a prerequisite of srpm-{dkms,kmod,utils} instead
of srpm-common, so that it will be done once before invoking the
recursive makes.

Also, gitrev is not really required for make dist, so instead of adding
it to BUILT_SOURCES, just add it as a prerequisite of the all target.

Mark the individual package targets as PHONY.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes #10564

Makefile.am

@@ -1,9 +1,5 @@
 ACLOCAL_AMFLAGS = -I config
 
-include config/rpm.am
-include config/deb.am
-include config/tgz.am
-
 SUBDIRS = include
 if BUILD_LINUX
 SUBDIRS += rpm
@@ -54,6 +50,7 @@ EXTRA_DIST += module/zfs/THIRDPARTYLICENSE.cityhash.descrip
 @CODE_COVERAGE_RULES@
 
 GITREV = include/zfs_gitrev.h
+CLEANFILES = $(GITREV)
 
 PHONY = gitrev
 gitrev:
@@ -68,10 +65,7 @@ gitrev:
 		mv -f $(GITREV)~ $(GITREV); \
 	fi
 
-$(GITREV): gitrev
-
-BUILT_SOURCES = $(GITREV)
-CLEANFILES = $(GITREV)
+all: gitrev
 
 # Double-colon rules are allowed; there are multiple independent definitions.
 distclean-local::
@@ -252,4 +246,8 @@ pkg-dkms: @DEFAULT_PACKAGE@-dkms
 pkg-kmod: @DEFAULT_PACKAGE@-kmod
 pkg-utils: @DEFAULT_PACKAGE@-utils
 
+include config/rpm.am
+include config/deb.am
+include config/tgz.am
+
 .PHONY: $(PHONY)