Allow opting our of apple_support completely

[jklukas]

We have developers that are often building locally on Mac laptops but don't have a full XCode installation. The current behavior of rules_graalvm is that it will always invoke apple_support.run when running on MacOS, which leads to an error if a full XCode installation is not available. By bypassing it, we're able to leverage toolchains_llvm for successful MacOS builds without XCode

My team is currently using a local patch to skip the following conditional branch where apple_support.run is called:

rules_graalvm/internal/native_image/rules.bzl

Lines 138 to 160 in 81fc9b2

	if is_macos:
	xcode_args = ctx.actions.args()
	# Bazel passes DEVELOPER_DIR and SDKROOT to every locally executed action that sets the
	# environment variables passed by apple_support.run. However, Graal sanitizes the
	# environment and removes these variables if set directly. We need to convert them into
	# -E options and rely on apple_support's argument replacement to pass them through to the
	# compiler invoked by Graal.
	# https://github.com/oracle/graal/blob/77a7f6a691024d22367ae33be4da0c15ceb6a246/substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/NativeImage.java#L1801-L1808
	xcode_args.add(apple_support.path_placeholders.xcode(), format = "-EDEVELOPER_DIR=%s")
	xcode_args.add(apple_support.path_placeholders.sdkroot(), format = "-ESDKROOT=%s")
	xcode_config = ctx.attr._xcode_config[apple_common.XcodeVersionConfig]
	# native-image reads the MACOSX_DEPLOYMENT_TARGET env var to determine target macos version
	run_params["env"]["MACOSX_DEPLOYMENT_TARGET"] = str(xcode_config.minimum_os_for_platform_type(apple_common.platform_type.macos))
	apple_support.run(
	actions = graal_actions,
	apple_fragment = ctx.fragments.apple,
	xcode_config = xcode_config,
	xcode_path_resolve_level = apple_support.xcode_path_resolve_level.args,
	arguments = [args, xcode_args],
	**run_params
	)

Would you consider a contribution that makes this use of apple_support.run configurable?