Use custom sqrt if stdc++ does not fall back to C99 csqrt (#54820)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54820
template implementation of std::sqrt() in libstdc++ yields incorrect results for `std::complex(-std::abs(x), -0.0)`, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89991
For example:
```
#include <iostream>
#include <complex>
int main() {
std::cout << std::sqrt(std::complex<float>(-1.0f, -0.0f)) << std::endl;
}
```
prints `(0, -1)` if libstdc++ is compiled to use C99 csqrt/csqrtf fallback, but `(0, 1)` if configured not to use it.
Test Plan: CI
Reviewed By: luciang
Differential Revision: D27379302
fbshipit-source-id: 03f614fdb7ff734139736a2a5f6872cee0173bee
