`M3DWrapper.h` is designed to omit the definition of `class M3DWrapper` if neither M3D import nor M3D export are compiled.
608bccd9cf touched the corresponding preprocessor checks and introduced a bug:
```
#ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
#if !(ASSIMP_BUILD_NO_EXPORT || ASSIMP_BUILD_NO_M3D_EXPORTER)
class M3DWrapper {
```
When compiling
- with M3D import enabled,
- but with either export generally disabled or M3D export disabled specifically,
These checks evaluate to the wrong result and skip the definition, leading to a build failure in dependent code.
```
#if 1 // import enabled
#if !(1 || 1) // export disabled and M3D export disabled
```
This commit fixes the check to compile the definition if neither import is disabled.
5cbc00a595