Fix for OpenMP offloading compilation error with GNU++20 option when using complex header (#115306)
The change done is to fix this issue.
[[Issue](https://github.com/llvm/llvm-project/issues/113207)] discussion
available in link provided.
When using the -std=c++20 flag with -fopenmp for OpenMP offloading
results in the following compilation error.
Reduced test Case :
```
> cat foo.cpp
#include <complex>
void foo(){
}
> CC -fopenmp -std=gnu++20 -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a foo.cpp -c
In file included from foo.cpp:1:
In file included from /opt/cray/pe/cce/18.0.1/cce-clang/x86_64/lib/clang/18/include/openmp_wrappers/complex:51:
/opt/cray/pe/cce/18.0.1/cce-clang/x86_64/lib/clang/18/include/openmp_wrappers/complex_cmath.h:68:40: error: non-constexpr declaration of 'conj' follows constexpr declaration
68 | template <class _Tp> std::complex<_Tp> conj(const std::complex<_Tp> &__c) {
| ^
/usr/lib64/gcc/x86_64-suse-linux/13/../../../../include/c++/13/complex:970:5: note: previous declaration is here
970 | conj(const complex<_Tp>& __z)
| ^
1 error generated.
```
Co-authored-by: Chandra Ghale <ghale@pe31.hpc.amslabs.hpecorp.net>
llvm-project
911cee2f - Fix for OpenMP offloading compilation error with GNU++20 option when using complex header (#115306)
