Introduce the concept of "target query" and "resolved target". A target
query is what the user specifies, with some things left to default. A
resolved target has the default things discovered and populated.
In the future, std.zig.CrossTarget will be rename to std.Target.Query.
Introduces `std.Build.resolveTargetQuery` to get from one to the other.
The concept of `main_mod_path` is gone, no longer supported. You have to
put the root source file at the module root now.
* remove deprecated API
* update build.zig for the breaking API changes in this branch
* move std.Build.Step.Compile.BuildId to std.zig.BuildId
* add more options to std.Build.ExecutableOptions, std.Build.ObjectOptions,
std.Build.SharedLibraryOptions, std.Build.StaticLibraryOptions, and
std.Build.TestOptions.
* remove `std.Build.constructCMacro`. There is no use for this API.
* deprecate `std.Build.Step.Compile.defineCMacro`. Instead,
`std.Build.Module.addCMacro` is provided.
- remove `std.Build.Step.Compile.defineCMacroRaw`.
* deprecate `std.Build.Step.Compile.linkFrameworkNeeded`
- use `std.Build.Module.linkFramework`
* deprecate `std.Build.Step.Compile.linkFrameworkWeak`
- use `std.Build.Module.linkFramework`
* move more logic into `std.Build.Module`
* allow `target` and `optimize` to be `null` when creating a Module.
Along with other fields, those unspecified options will be inherited
from parent `Module` when inserted into an import table.
* the `target` field of `addExecutable` is now required. pass `b.host`
to get the host target.
This moves many settings from `std.Build.Step.Compile` and into
`std.Build.Module`, and then makes them transitive.
In other words, it adds support for exposing Zig modules in packages,
which are configured in various ways, such as depending on other link
objects, include paths, or even a different optimization mode.
Now, transitive dependencies will be included in the compilation, so you
can, for example, make a Zig module depend on some C source code, and
expose that Zig module in a package.
Currently, the compiler frontend autogenerates only one
`@import("builtin")` module for the entire compilation, however, a
future enhancement will be to make it honor the differences in modules,
so that modules can be compiled with different optimization modes, code
model, valgrind integration, or even target CPU feature set.
closes#14719
