C Command sample fails to build with CMake

### This issue is for a: (mark with an `x`)
```
- [ X] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce

- create a new codespace from this repo
- select C command configuration

### Any log messages given by the failure

```
[cmake] CMake Error at scenarios/command/c/CMakeLists.txt:14 (add_executable):
[cmake] Cannot find source file:
[cmake]
[cmake] /workspaces/MqttApplicationSamples/scenarios/command/c/protobuf/google/protobuf/timestamp.pb-c.c
[cmake]
[cmake] Tried extensions .c .C .c++ .cc .cpp .cxx .cu .mpp .m .M .mm .ixx .cppm
[cmake] .ccm .cxxm .c++m .h .hh .h++ .hm .hpp .hxx .in .txx .f .F .for .f77 .f90
[cmake] .f95 .f03 .hip .ispc
[cmake]
[cmake]
[cmake] CMake Error at scenarios/command/c/CMakeLists.txt:14 (add_executable):
[cmake] No SOURCES given to target: command_server
[cmake]
[cmake]
[cmake] CMake Error at scenarios/command/c/CMakeLists.txt:22 (add_executable):
[cmake] No SOURCES given to target: command_client
[cmake]
[cmake]
[cmake] CMake Generate step failed. Build files cannot be regenerated correctly.
[proc] The command: /home/codespace/.local/bin/cmake -DCMAKE_BUILD_TYPE=Debug -DPRESET_PATH=/workspaces/MqttApplicationSamples/scenarios/command/c -S/workspaces/MqttApplicationSamples -B/workspaces/MqttApplicationSamples/scenarios/command/c/build -G Ninja exited with code: 1
```

### Expected/desired behavior
The sample builds successfully

### Language
> C

### OS and Version?
> Codespaces

### Mention any other details that might be useful

Other targets build correctly
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