exernal_project: Fix default cross compile parameters
The variable `{host}` cannot be successfully expanded.
Using the `@HOST@` parameter, as suggested by the documentation, works.
@@ -261,7 +261,7 @@ class ExternalProjectModule(ExtensionModule):
raise InterpreterException('add_project takes exactly one positional argument')
configure_command = args[0]
configure_options = kwargs.get('configure_options', [])
- cross_configure_options = kwargs.get('cross_configure_options', ['--host={host}'])
+ cross_configure_options = kwargs.get('cross_configure_options', ['--host=@HOST@'])
verbose = kwargs.get('verbose', False)
env = self.interpreter.unpack_env_kwarg(kwargs)
project = ExternalProject(self.interpreter,
