Explicitly break unit-tests foreach into for loop.

It seems that in some env if the path is large enough for the full list
of files, the full bash command in that target gets too big for bash and
hence will trigger an error ``too many arguments``.

Signed-off-by: Weilong Cui <cuiwl@google.com>

Makefile

@@ -146,9 +146,14 @@ ifeq ($(SKIP_VET),"false")
 endif
 	$(QUIET) echo "mode: count" > coverage-all-tmp.out
 	$(QUIET) echo "mode: count" > coverage.out
-	$(QUIET)$(foreach pkg,$(patsubst %,github.com/cilium/cilium/%,$(TESTPKGS)),\
-		$(_GO) test $(GOFLAGS) $(TEST_UNITTEST_LDFLAGS) $(pkg) $(GOTEST_BASE) $(GOTEST_COVER_OPTS) || exit 1; \
-		tail -n +2 coverage.out >> coverage-all-tmp.out;)
+	# It seems that in some env if the path is large enough for the full list
+	# of files, the full bash command in that target gets too big for bash and
+	# hence will trigger an error of too many arguments. As a workaround, we
+	# have to process these packages in different subshells.
+	for pkg in $(patsubst %,github.com/cilium/cilium/%,$(TESTPKGS)); do \
+		$(_GO) test $(GOFLAGS) $(TEST_UNITTEST_LDFLAGS) $$pkg $(GOTEST_BASE) $(GOTEST_COVER_OPTS) || exit 1; \
+		tail -n +2 coverage.out >> coverage-all-tmp.out; \
+	done
 	$(MAKE) generate-cov
 	@rmdir ./daemon/1 ./daemon/1_backup 2> /dev/null || true
 	$(MAKE) stop-kvstores