fix: Relax exec_compatible_with requirement on dtrace rules.

[mkosiba]

In #2661 the exec_compatible_with was added. This breaks some of our Linux-based tests where we use systemtap dtrace. I was hoping we could move the constraint onto the tool itself (that way we can supply one that's Linux-compatible and things keep working).target_compatible_with works for my usecase, but it's not exactly the same as the previous solution. @brentleyjones, could you have a look and let me know if this works for you?

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[brentleyjones]

target_compatible_with doesn't influence toolchain selection, which is what is needed for exec_compatible_with. So some form of exec_compatible_with will be needed still.

[mkosiba]

@brentleyjones, can you explain a bit more about toolchain selection for dtrace_compile? AFAICT the dtrace binary path is hardcoded (so not affected by toolchain resolution). Or is it that you have both macos and linux remote workers available and want to make sure this rule only runs on the macos workers?

[brentleyjones]

Or is it that you have both macos and linux remote workers available and want to make sure this rule only runs on the macos workers?

Something like that. We initiate our builds from Linux, to run on macOS executors, and without this change it could select Linux exectors.

[mkosiba]

ok, so I think using a toolchain (as the updated PR now does) should work for that setup. I did a bit of testing:

• if --host_platform=linux then the build fails with a toolchain resolution error (I'm assuming that's OK from a UX perspective),
• if --host_platform=linux --extra_execution_platforms=linux,macos then the macos platform gets chosen for the rule, so this should have similar behavior to setting exec_compatible_with on the rule,
• if --host_platform=macos then this works without any extra configuration.

I'm happy to toolchain-ify the other rules that have exec_compatible_with set if you'd like me to (I don't think there is benefit to this other than consistency).

[brentleyjones]

Neat!

I'm happy to toolchain-ify the other rules that have exec_compatible_with set if you'd like me to (I don't think there is benefit to this other than consistency).

Only a benefit if we are using a path that we want to override.