since a9438d1f5e, project introduced alloca calls.
but in [BSD manpage][1], this function is machine and compiler dependent.
also if use newlib or glibc, this function requires `alloca.h` unlike bsd
system.
this patch just revert alloca call except MSC case.
[1]: https://www.freebsd.org/cgi/man.cgi?alloca
41248aad1e