As described in autoconf-archive upstream [1], from where
`build/ax_gcc_func_attribute.m4` is forked, the old unknown func attr
detection method would throw a false negative anytime an unrelated
warning was raised.
This results in `ax_cv_have_func_attribute_target` being set to `no`
whenever certain compiler Warning flags are switched on. Namely, having
`-Wall` on, which is a default CFLAG for some linux distributions, will
result in
```
warning: ‘bar’ declared ‘static’ but never defined [-Wunused-function]
```
when evaluating support for the `target` function attribute.
With that configuration value set to `no`, the compiled php binaries
will not support x86_64 v3 instructions such as avx2 and sse2, which
should speed up specific tasks ran by PHP.
This issue was originally reported in Ubuntu [2].
[1] http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=commitdiff;h=df0894ad1a8195df67a52108b931e07d708cec9a
[2] https://bugs.launchpad.net/ubuntu/+source/php8.1/+bug/1882279
Closes GH-8483.
