sandbox: Do not silently drop platform properties

For remote execution, there is currently no way to determine what
platform properties are supported. Silently dropping platform properties
that may or may not be supported can result in build behavior
differences or confusing errors.

This code was originally added before the `build-uid` and `build-gid`
sandbox configuration was made optional to not break remote execution.
However, now that the corresponding platform properties are only set if
requested by the project or element, it's better to fail the build than
to ignore the setting.

Author: juergbi

src/buildstream/sandbox/_sandboxbuildboxrun.py

@@ -238,6 +238,3 @@ def resume_proc():
 
             if returncode != 0:
                 raise SandboxError("buildbox-run failed with returncode {}".format(returncode))
-
-    def _supported_platform_properties(self):
-        return {"OSFamily", "ISA", "unixUID", "unixGID", "network"}

src/buildstream/sandbox/_sandboxreapi.py

@@ -131,10 +131,6 @@ def _create_platform(self, flags):
         if flags & _SandboxFlags.NETWORK_ENABLED:
             platform_dict["network"] = "on"
 
-        # Remove unsupported platform properties from the dict
-        supported_properties = self._supported_platform_properties()
-        platform_dict = {key: value for (key, value) in platform_dict.items() if key in supported_properties}
-
         # Create Platform message with properties sorted by name in code point order
         platform = remote_execution_pb2.Platform()
         for key, value in sorted(platform_dict.items()):
@@ -203,9 +199,6 @@ def _create_batch(self, main_group, flags, *, collect=None):
     def _execute_action(self, action, flags):
         raise ImplError("Sandbox of type '{}' does not implement _execute_action()".format(type(self).__name__))
 
-    def _supported_platform_properties(self):
-        return {"OSFamily", "ISA"}
-
 
 # _SandboxREAPIBatch()
 #