Don't run shellcheck in make all

I don't think users (through sxmo-build, for example) need to run
shellcheck just to install this. Note that .build.yml still runs it.

Signed-off-by: Maarten van Gompel <proycon@anaproy.nl>

Makefile

@@ -9,7 +9,7 @@ PROGRAMS = \
 	programs/sxmo_megiaudioroute \
 	programs/sxmo_vibratepine
 
-all: shellcheck $(PROGRAMS)
+all: $(PROGRAMS)
 
 shellcheck:
 	shellcheck -x scripts/*/*