Fix version.h generation

Currently the build fails when parallelised with:

  make[1]: *** No rule to make target 'version.h', needed by 'util.o'.  Stop.

Fix the name of the Makefile dependency to fix the build error.

Fixes: #91
Closes: #92
Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>

Author: obbardc

Makefile

@@ -34,7 +34,7 @@ versionfile:
 	@echo "#define VERSION \"$(GITREF)\"" > .version.h
 	@cmp -s .version.h version.h || cp .version.h version.h
 
-util.o: version.h
+util.o: versionfile
 
 clean:
 	rm -f $(QDL) $(QDL_OBJS)