Add test-stdlib and test-stdlib-debug targets to Makefile (#2456)
Add test-stdlib and test-stdlib-debug targets to Makefile (#2456)

The targets can be used to test issue #2451

These use the sub-targets stdlib-debug, stdlib to compile stdlib either
in debug or not. 

sgebbie/ponyc,Theodus/ponyc,dipinhora/ponyc,ponylang/ponyc,ponylang/ponyc,dipinhora/ponyc,ponylang/ponyc,cquinn/ponyc,kulibali/ponyc,CausalityLtd/ponyc,Theodus/ponyc,Theodus/ponyc,cquinn/ponyc,sgebbie/ponyc,Theodus/ponyc,Praetonus/ponyc,cquinn/ponyc,jemc/ponyc,Theodus/ponyc,Praetonus/ponyc,CausalityLtd/ponyc,jemc/ponyc,Praetonus/ponyc,Praetonus/ponyc,sgebbie/ponyc,kulibali/ponyc,cquinn/ponyc,CausalityLtd/ponyc,kulibali/ponyc,sgebbie/ponyc,sgebbie/ponyc,jemc/ponyc,dipinhora/ponyc,kulibali/ponyc