Compilation error with Apple Clang 17.0.0

Per the title, building GauXC with Apple Clang 17.0.0 results in the compilation error: ``` [build] .../src/xc_integrator/integrator_util/spherical_harmonics.cxx:143:31: error: no member named 'sph_legendre' in namespace 'std' [build] 143 | double sph = std::sph_legendre(l, m, theta) * ratio; [build] | ~~~~~^ ``` which looks like it was added in 66784a442141fe2c4e14957337be054b77c2a5bb. FWIW, I did try adding `#include <cmath>`, but that didn't solve the problem. A quick Google search suggests that these functions were at one point an issue in normal LLVM (e.g., [here](https://stackoverflow.com/questions/43017891/how-to-compile-special-mathematical-functions-with-clang)), but that issue is quite old and seems to have been fixed now (as evidenced by GauXC's LLVM CI passing). I came up empty when looking for Apple Clang specifically.