Backport 43470:

Backport 43470:
Get gcc to do strict IEEE math.  This flag was already used for cc, just not
gcc.  Without this flag, doing pretty much anything with NaNs causes
a Floating Point Exception signal.  This causes the interpreter to quit.
The failing tests this fixes are:  test_long.
This is somewhat equivalent to doing signal(SIGFPE, SIG_IGN).