feat: update depot version and enhance host build support

- Bump the version of the "depot" package from 0.26.1 to 0.27.0 in Cargo.toml and Cargo.lock.
- Modify meson.build, autotools.rs, cmake.rs, custom.rs, makefile.rs, and other builder files to include a new parameter for host build directory.
- Implement logic to handle host builds across various build systems (Autotools, CMake, Meson).
- Add tests to ensure that environment variables for host build directories are correctly expanded.
- Introduce new flags in PackageSpec to control host build behavior.

src/builder/python.rs

@@ -32,6 +32,7 @@ pub fn build(
     destdir: &Path,
     cross: Option<&CrossConfig>,
     export_compiler_flags: bool,
+    _host_build_dir: Option<&Path>,
 ) -> Result<()> {
     let flags = &spec.build.flags;
     let actual_src = resolve_actual_src(spec, src_dir)?;