package/pkg-generic.mk: fix rule order for reinstall/rebuild/reconfigure

The reinstall, rebuild and reconfigure commands rely on the
left-to-right order of evaluation of the dependencies to make sure that
the stamp files are removed before attempting to rebuild. However, this
order of evaluation is not guaranteed. In particular, if top-level
parallel build is enabled, they are executed in parallel and the stamp
file may not have been removed yet when it is evaluated to decide if
rebuild has to be done.

Since make 4.4, it is possible to reproduce this issue by passing
`--shuffle=reverse` to the make commandline.

To solve this, add a .WAIT directive between the clean and
install/build/configure dependencies. .WAIT was introduced in make 4.4
as well. It makes sure that the dependencies on the left are evaluated
before the dependencies on the right - exactly what we want here.

Earlier versions of make don't know about .WAIT, so we need to add a
.PHONY dependency to effectively ignore it.

Note that this doesn't fix the problem for make versions earlier than
4.4. However, the issue isn't really that important: reinstall, rebuild
and reconfigure are development tools, they're not fully reliable to
begin with, and it's anyway less likely that someone uses `make -j` when
doing a reinstall/rebuild/reconfigure.

Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
Reported-by: James Hilliard <james.hilliard1@gmail.com>

Makefile

@@ -1260,4 +1260,7 @@ include docs/manual/manual.mk
 
 .PHONY: $(noconfig_targets)
 
+# .WAIT was introduced in make 4.4. For older make, define it as phony.
+.PHONY: .WAIT
+
 endif #umask / $(CURDIR) / $(O)

package/pkg-generic.mk

@@ -1063,17 +1063,17 @@ endif
 			rm -f $$($(2)_TARGET_INSTALL_IMAGES)
 			rm -f $$($(2)_TARGET_INSTALL_HOST)
 
-$(1)-reinstall:		$(1)-clean-for-reinstall $(1)
+$(1)-reinstall:		$(1)-clean-for-reinstall .WAIT $(1)
 
 $(1)-clean-for-rebuild: $(1)-clean-for-reinstall
 			rm -f $$($(2)_TARGET_BUILD)
 
-$(1)-rebuild:		$(1)-clean-for-rebuild $(1)
+$(1)-rebuild:		$(1)-clean-for-rebuild .WAIT $(1)
 
 $(1)-clean-for-reconfigure: $(1)-clean-for-rebuild
 			rm -f $$($(2)_TARGET_CONFIGURE)
 
-$(1)-reconfigure:	$(1)-clean-for-reconfigure $(1)
+$(1)-reconfigure:	$(1)-clean-for-reconfigure .WAIT $(1)
 
 # define the PKG variable for all targets, containing the
 # uppercase package variable prefix