build.make: skip shellcheck if Docker is not available
Not all environments have Docker. The simplifying assumption here is
that if the Docker command is available, it's also usable.
@@ -141,6 +141,10 @@ test: test-shellcheck
test-shellcheck:
@ echo; echo "### $@:"
@ ret=0; \
+ if ! command -v docker; then \
+ echo "skipped, no Docker"; \
+ return 0; \
+ fi; \
for dir in $(abspath $(TEST_SHELLCHECK_DIRS)); do \
echo; \
echo "$$dir:"; \
