This CL is an alternative to unknown commit. I left the other CL seperately, because I wasn't 100% sure that we'd agree to this, since this is an API change.
I did it this way because I believe it's much less hacky, and it also allows us to format things that aren't variables.
BEGIN_PUBLIC
Add support for select'ing on cc_args(args=...).
This is quite tricky because the one parameter was being split into two in a macro, one of type label and the other of type string.
For example, `args = ["--foo", format_arg("--bar=%s", "//path/to:bar")]` was rewritten by the macro to `args = [json.encode(struct(format_type="raw", format="foo")), json.encode(struct(format_type="format_arg", format="--bar=%s", value=0))], variables = ["//path/to:bar"]`.
To allow it to work with selects, we need to ensure that we don't perform post-processing on the inside of the select. To solve this, we:
* Ensure that args only take strings
* Provide a seperate parameter for substitutions.
This new mechanism also has the useful property that we can now format things that are not variables. For example, I can do the following:
```
directory(name = "sysroot", ...)
cc_args(
name = "sysroot_arg",
args = ["--sysroot={sysroot}"],
format = {
":sysroot": "sysroot"
}
)
```
END_PUBLIC
PiperOrigin-RevId: 656211278
Change-Id: If83f1ea5a99090c18f2a561c51ec6d39ce9fe419
BEGIN_PUBLIC
Implement flag_group in the new rule-based toolchain.
END_PUBLIC
PiperOrigin-RevId: 622107179
Change-Id: I9e1971e279f313ce85537c899bcf80860616f8b7
BEGIN_PUBLIC
Improve errors in variable definitions by adding labels to the variables.
END_PUBLIC
PiperOrigin-RevId: 618984216
Change-Id: I5d6d11ba2b72f426b9f01bcbb528b0914c98c964
BEGIN_PUBLIC
Add strictly typed variables to toolchain rules.
This should allow us to implement a proper replacement for flag_group
END_PUBLIC
PiperOrigin-RevId: 617338607
Change-Id: I7f3058578cb5eb17ecc1aa38d2e1459e0742aee9
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