Fun fact: your Makefile above is redundant. You can delete it entirely, and the implicit rules you're using here continue to work just fine.
dima@fatty:/tmp$ mkdir dir
dima@fatty:/tmp$ cd dir
dima@fatty:/tmp/dir$ touch foo.c
dima@fatty:/tmp/dir$ make -n foo
cc foo.c -o foo
dima@fatty:/tmp/dir$ make --version
GNU Make 4.1
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. make foo.c
Should just work. No makefile needed. make foo
or make foo.o