NativeExecutableSpec should have default toolchains which target MacOS Intel and ARM

[prbprbprb]

Expected Behavior

Consider a trivial native project:

plugins {
    id 'cpp'
}

model {
    components {
        hello(NativeExecutableSpec) {
            targetPlatform "osx_x86-64"
            targetPlatform "osx_aarch64"

            sources {
                cpp {
                   source {
                     srcDir "src/cpp"
                     include "hello.cc"
                   }
                }
            }
        }
    }
}

Ideally this should build out of the box on either Intel or ARM based Macs with no further configuration.

Current Behavior

1. Failure with Invalid NativePlatform: osx_aarch64
2. After removing targetPlatform "osx_aarch64" then gradle components thinks it is targetting osx_x86-64 (expected) but on an ARM based Mac gradle build will actually build native ARM executables as no -arch flag is passed to Clang.

This can be overcome by adding the toolchain definitions manually (see attached project) but ideally shouldn't be necessary,
e.g.

    toolChains {
        clang(Clang) {
            target("osx_aarch64") {
                cppCompiler.withArguments { args ->
                    args << "-arch" << "arm64"
                }
     [... and so on for linker and Intel targets ...]

Context

Adding ARM support for another project: google/conscrypt#1034 - both the JNI libs and the generated source need local toolchain definitions to build at all on MacOS ARM.

In general it makes developing on an M1 based Mac more painful.

Steps to Reproduce (for bugs)

Simple project attached. hellonative.tar.gz

Will fail out of the box or work after uncommenting the toolchain definitions.

I also have a PR I am about to submit with a working fix for this.

Your Environment

Gradle 7.4.1 and locally built from source.

Also affects 6.x, and 6.x has the further issue that the target platform type for ARM-based Macs is inferred as osx_arm-v8 rather than osx_aarch64. [Update: looks like this is fixed in 6.9.1]