BUILD: makefile: fix range build without test command

BUILD: makefile: fix range build without test command

In 3.3, the "make range" target adopted a test command via the TEST_CMD
variable, with commit 90b70b61b1 ("BUILD: makefile: implement support
for running a command in range"). However now it breaks the script when
TEST_CMD is not set due to the shell expansion leaving two '||' operators
side by side. Let's fix this by passing the contents of the makefile
variable in positional arguments before executing them.