Add support for M1 Mac (ARM)

[vjspranav]

Having -march=x86-64 in utilities.rkt seems to be causing issue with aarch64 M1 architecture
The error on running make-test:
The clang compiler doesn't support "-march=-x86-64"

[rundong08]

Here's a workaround:
To compile the runtime.c file to get runtime.o:

cc -arch x86_64 -march=x86-64 -c runtime.c

And in utilities.rkt, add the -arch x86_64 option to the corresponding gcc call.

Note on M1 mac -march=x86-64 is only available when you use -arch x86_64 option.