(apro) build-aux: Avoid needing things in build-aux/bin/ during clean…

… & clobber

So, I run `make clobber`.

common.mk says:

    clobber: clean

The 'clean' target wants to run

    ./build-aux/bin/gubernaut -release $$(cat $*.knaut.claim)

prelude.mk says:

    clobber: _clobber-prelude

The '_clobber-prelude' target wants to run

   rm -rf ./build-aux/bin

Because there is no ordering between dependencies of 'clobber', it is
possible that '_clobber-prelude' deletes bin/gubernaut before 'clean'
tries to run bin/gubernaut.

Avoid this by using `go run` instead of binaries when doing cleanup rules.

This is very awkward and gross because of having to cd to get the correct
Go module, and then that makes us use $(abspath) for file arguments.

CHANGELOG.md

@@ -1,6 +1,9 @@
 <!-- -*- fill-column: 100 -*- -->
 # Datawire build-aux CHANGELOG
 
+ - 2019-08-13: Fix race condition in `make clobber` where it attempted to use compiled programs used
+               for cleanup, after the programs themselves had already been deleted.
+
  - 2019-07-10: `var.mk`: Introduce
 
  - 2019-07-05: `build-aux-push`: Work around problem with `git subtree`; avoid accidentally pushing

HACKING.md

@@ -20,6 +20,14 @@
    value.
  - Make sure to pass `--fail` to `curl` when downloading things;
    otherwise it will silently save 404 HTML/XML pages.
+ - Don't depend on anything in ./build-aux/bin/ during clean and
+   clobber rules.  The `prelude.mk` cleanup might remove it before
+   your cleanup bit runs.  For Go programs, `cd` to the program's
+   sourcedirectory, and use `go run .` to run it:
+
+		cd $(dir $(_myfile.mk))bin-go/PROGRAM && GO111MODULE=on go run . ARGS...
+
+   Only tolerate that grossness in your cleanup rules.
 
 ## Naming conventions
 

docker.mk

@@ -158,8 +158,11 @@ _docker.port-forward = $(dir $(_docker.mk))docker-port-forward
 	docker push '$(DOCKER_IMAGE)'
 .PHONY: %.docker.push
 
-_clean-docker: $(FLOCK)
-	$(FLOCK) $(_docker.port-forward).lock rm $(_docker.port-forward).lock
+# This `go run` bit is gross, compared to just depending on and using
+# $(FLOCK).  But if the user runs `make clobber`, the prelude.mk
+# cleanup might delete $(FLOCK) before we get to run it.
+_clean-docker:
+	cd $(dir $(_docker.mk))bin-go/flock && GO111MODULE=on go run . $(abspath $(_docker.port-forward).lock) rm $(abspath $(_docker.port-forward).lock)
 	rm -f $(_docker.port-forward).log
 	rm -f $(dir $(_docker.mk))docker-registry.yaml.o
 clean: _clean-docker

kubernaut.mk

@@ -56,8 +56,11 @@ GUBERNAUT ?= $(build-aux.bindir)/gubernaut
 	$(GUBERNAUT) -release $$(cat $<)
 	$(GUBERNAUT) -claim $$(cat $<) -output $@
 
-%.knaut.clean: $(GUBERNAUT)
-	if [ -e $*.knaut.claim ]; then $(GUBERNAUT) -release $$(cat $*.knaut.claim); fi
+# This `go run` bit is gross, compared to just depending on and using
+# $(GUBERNAUT).  But if the user runs `make clobber`, the prelude.mk
+# cleanup might delete $(GUBERNAUT) before we get to run it.
+%.knaut.clean:
+	if [ -e $*.knaut.claim ]; then cd $(dir $(_kubernaut.mk))bin-go/gubernaut && GO111MODULE=on go run . -release $$(cat $(abspath $*.knaut.claim)); fi
 	rm -f $*.knaut $*.knaut.claim
 .PHONY: %.knaut.clean