[eclass] Depend on ECM git master to fix QM loader build errors

Current ECM 0.0.12 doesn't provide `ecm_create_qm_loader` which results in:
```
CMake Error at src/solid/CMakeLists.txt:49 (ecm_create_qm_loader):
  Unknown CMake command "ecm_create_qm_loader".
```
for those KF5 components making use of `ecm_create_qm_loader`.