Build fails when using the Green Hills MULTI generator

### Brief Issue Summary

The default target for gbuild and Green Hills MULTI should be ALL_BUILD, not all. ALL_BUILD is the same Utility target used by Visual Studio generators.

```
[build] Starting build
[proc] Executing command: /opt/cmake/bin/cmake --build /home/XXX/Projects/bin_dir --config Debug --target all -j 6 --
[build] Building all.tgt.gpj
[build] Could not find: all.tgt.gpj within: amcs_oe_sdk.top.gpj
[build] Not all requested files were built. Skipped: all.tgt.gpj
[build] Done
```

### CMake Tools Diagnostics

```shell

```

### Debug Log

```shell

```

### Additional Information

_No response_

Inspect the CMake Tools code that selects the default build target for gbuild and the Green Hills MULTI generator; no specific file or test is named in the issue. Reproduce the shown cmake --build command, then verify that the selected target is ALL_BUILD and that the corresponding build succeeds.

Written by the indexing model from the issue text.