[feat] More intuitive error description

[Routhleck]

braintaichi/braintaichi/_primitive/_mlir_translation_rule.py

Lines 243 to 244 in 958463c

	if ti.lang.impl.current_cfg().arch != arch:
	raise RuntimeError(f"Arch {arch} is not available")

If there is no target environment specified as GPU/CUDA, the error message should suggest that the issue might be due to the absence of a CUDA environment.

See #46