x-svr4

早期freebsd实现

# Some versions of SVR4 have an alloca in /usr/ucblib/libucb.a, and if we are
# careful to link that in after libc we can use it, but since newer versions of
# SVR4 are dropping libucb, it is better to just use the portable C version for
# bootstrapping.  Do this by defining ALLOCA.

ALLOCA = alloca.o