docker: pass EXECUTABLE to build script

To build a docker image with which needs qemu linux-user emulation we
need to pass --include-executable to the build script. Using the same
mechanism as for other container controls we enable the option is
EXECUTABLE is set on the make command line e.g:

    make docker-image-debian-bootstrap V=1 J=9 DEB_ARCH=armhf \
        DEB_TYPE=stable EXECUTABLE=./arm-linux-user/qemu-arm

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1468934445-32183-11-git-send-email-famz@redhat.com
Signed-off-by: Fam Zheng <famz@redhat.com>
diff --git a/tests/docker/Makefile.include b/tests/docker/Makefile.include
index e7f0023..78af468 100644
--- a/tests/docker/Makefile.include
+++ b/tests/docker/Makefile.include
@@ -46,7 +46,8 @@
 docker-image-%: $(DOCKER_FILES_DIR)/%.docker
 	$(call quiet-command,\
 		$(SRC_PATH)/tests/docker/docker.py build qemu:$* $< \
-		$(if $V,,--quiet) $(if $(NOCACHE),--no-cache),\
+		$(if $V,,--quiet) $(if $(NOCACHE),--no-cache) \
+		$(if $(EXECUTABLE),--include-executable=$(EXECUTABLE)),\
 		"  BUILD $*")
 
 # Expand all the pre-requistes for each docker image and test combination
@@ -95,6 +96,7 @@
 	@echo '    DEBUG=1              Stop and drop to shell in the created container'
 	@echo '                         before running the command.'
 	@echo '    NOCACHE=1            Ignore cache when build images.'
+	@echo '    EXECUTABLE=<path>    Include executable in image.'
 
 docker-run-%: CMD = $(shell echo '$@' | sed -e 's/docker-run-\([^@]*\)@\(.*\)/\1/')
 docker-run-%: IMAGE = $(shell echo '$@' | sed -e 's/docker-run-\([^@]*\)@\(.*\)/\2/')