Please revert b2e843161d

Can someone with commit access please revert b2e843161dc3b?

    git log -r b2e843161dc3b79777e873183447c92ed9c3703a
    Author: Andrew Turner <andrew@FreeBSD.org>
    Date:   Tue Nov 2 11:31:17 2021 +0000

    Use a builtin where possible in msun


If one has a libm built with, e.g., -DUSE_BUILTIN_FMAF,
and then tries to debug code that uses fmaf() where the
compiler options include -fno-builtin, a segfault
occurs.  I suggest purging all of the recent additions
of USE_BUILTIN_*.  These are simply not needed as a compiler
will use a builtin (if available) instead of a function from
libm.

% cat t5.c
#include <math.h>
#include <stdio.h>

int
main(void)
{
    float x;
    x = fmaf(0.9474001f, 4.639901e-7f, -0.24325085f);
    printf("%la\n", x);
    return (0);
}

% cc -o z -fno-builtin -g t5.c -lm && ./z
Segmentation fault (core dumped)

% gdb151 ./z
(gdb) run
Starting program: /home/kargl/tmp/z

Program received signal SIGSEGV, Segmentation fault.
Invalid permissions for mapped object.
0x0000000000201694 in fmaf ()

PS: t5.c reveals a bug in the software implementation of s_fmaf.c

-- 
steve