BUILD: Makefile: force $(shell command -v ...) to run through the shell

BUILD: Makefile: force $(shell command -v ...) to run through the shell

$(shell) commands with no metacharacter and not starting with a shell
builtin may be execvp()'d directly instead of being run through the
shell. "command" is a shell builtin that only appears in make's own
builtin list since version 4.3, so with make <= 4.2 the USE_MINIDEBUG
probe failed with "Command not found" and silently disabled the
embedded symbol table. Adding "2>/dev/null || :" brings metacharacters
which force the shell path on all make versions.

This should fix build on older distributions such as Ubuntu 18.04.