Makefile: simple makefile to run tests (go, gccgo, clang, gcc)

simple makefile to enable running a bunch of tests:

```sh
$ make go gccgo clang gcc
go build -compiler=gc -o run-gcgo Go.go 
time (./run-gcgo -v=1234 &> /dev/null)

real	0m1.855s
user	0m1.843s
sys	0m0.010s

go build -compiler=gccgo -gccgoflags="-O3" -o run-gccgo Go.go
time (./run-gccgo -v=1234 &> /dev/null)

real	0m0.712s
user	0m0.693s
sys	0m0.017s

clang -o run-clang -O3 C.c
time (./run-clang 1234 &> /dev/null)

real	0m0.466s
user	0m0.463s
sys	0m0.000s

gcc -o run-gcc -O3 C.c
time (./run-gcc 1234 &> /dev/null)

real	0m0.493s
user	0m0.487s
sys	0m0.003s
```