[CM] [SPAM:####] Failed to disable HAVE_OVERFLOW_CHECKS

[bil at ccrma.Stanford.EDU]

HAVE_OVERFLOW_CHECKS is not defined by the compilers.  You can see what
is defined by

   touch foo.h
   cpp -dM foo.h

where foo.h should be empty.

To build s7 without overflow checks in gcc/linux:

gcc s7.c -c -I. -DHAVE_OVERFLOW_CHECKS=0 -ldl -lm -Wl,-export-dynamic

Then, (using the repl based on that s7):

<1> (+ 9223372036854775807 1)
-9223372036854775808

whereas with those checks:

<1> (+ 9223372036854775807 1)
9223372036854776000.0

s7test.scm will also show many other differences.