Drop old compilers from CI
and update compiler version checks in CMake
| compiler | minimum | current |
|---|---|---|
| Intel | 2017 | 2019 |
| GCC | 5 | 8 |
| Clang | 4 | 7 |
| MSVC | 2017 | ? |
Minimum CUDA version for C++14 is 9.0 So use the appropriate CUDA versions for each compiler.
| CUDA | GCC | Clang | Intel |
|---|---|---|---|
| 9.0 | 5-6 | none | 17 |
| 9.1 | 5-6 | 4 | 17 |
| 9.2 | 5-7 | 4-5 | 17 |
| 10.0 | 5-7 | 4-6 | 17-18 |