feat: extended native-image build options

[sgammon]

Summary

Adds more integration points with Bazel's build settings. Initial Platforms stuff might happen in this PR too. Targeting #80 for release if possible (we'll see).

Not yet implemented:
Needs integration with Bazel's Platforms feature, and transition implementations.

Related issues:

• Bazel Settings Propagation #78
• Better control of -march #89
• Native Image options parity #108

Usage

There is a new native_image_settings target, which can be used to specify an explicit bundle of Native Image compilation settings:

load(
  "@rules_graalvm//graalvm:defs.bzl",
  "NativeCompilerBackend",
  "NativeLibC",
  "NativeArchitecture",
  "NativeOptimization",
  "native_image_settings",
)

native_image_settings(
    name = "cool_settings",
    backend = NativeCompilerBackend.LLVM,  # or `NATIVE`
    libc = NativeLibC.GLIBC,  # or `MUSL`
    opt = NativeOptimization.FASTBUILD,  # or `OFF`, `DEFAULT`, or `OPTIMIZATION_LEVEL_[1|2]`
    arch = NativeArchitecture.NATIVE,  # or `COMPATIBILITY`, `AMD_64`, `ARM_64`
)

native_image(
  name = "my_binary",
  # ...
  settings = ":cool_settings",
)

Overriding options via Bazel Configurations

native_image_settings(
    name = "cool_settings",
    arch = NativeImageArchitecture.NATIVE,  # or `COMPATIBILITY`, `AMD_64`, `ARM_64`

    # (`settings` is implied by default, pass `None` to opt-out)
    settings = "@rules_graalvm//graalvm/native_image:defaults",
)

If you do nothing at all, or map the settings property this way (or provide your own equivalent native_image_info advice target), then certain flags will override your native_image_settings. With the above configuration, settings are effectively resolved from the following places, in order:

1) Overrides provided by the command line, like below
2) Explicit settings declared in the mapped `native_image_settings` bundle
3) Sensible defaults provided by `rules_graalvm` (for example, `compilation_mode` → `O[x]`)

This allows you to set a default march, for instance:

native_image_settings(
  name = "settings",
  arch = NativeArchitecture.COMPATIBILITY,
)

native_image(
  # ...
  settings = ":settings",
)

Which you can override easily on the command line when desired:

bazel build //your/native:target --@rules_graalvm//graalvm/nativeimage/options:arch=native

How you know it's working

In the native-image build output, the target machine will be set accordingly:

bazel build //your/native:target --@rules_graalvm//graalvm/nativeimage/options:arch=native

========================================================================================================================
GraalVM Native Image: Generating 'main-native-bin' (executable)...
========================================================================================================================
For detailed information and explanations on the build output, visit:
https://github.com/oracle/graal/blob/master/docs/reference-manual/native-image/BuildOutput.md
------------------------------------------------------------------------------------------------------------------------
[1/8] Initializing...                                                                                    (2.7s @ 0.17GB)
 Java version: 20.0.2+9, vendor version: GraalVM CE 20.0.2+9.1
 Graal compiler: optimization level: b, target machine: native

...

Opting out of rules-controlled flags

To remove (some) of the Rules-controlled flags and instead withhold them or provide them via extra_args, you can pass None to the settings attribute, which prevents override:

native_image_settings(
    name = "minimal",
    settings = None,
)

native_image(
  # ...
  settings = ":minimal",
)

In this case, these flags are withheld from automatic injection, although you may still need to provide some of them to complete a native-image build. Effectively, most flags take on GraalVM's defaults.

Changelog

• feat: add experimental build setting which controls the march parameter

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[sgammon]

closing for now