Make rustup a requirement and switch to `rust-toolchain.toml` (#30056)

This change makes rustup a requirement for building Servo with `./mach`
and switches to the newer `rust-toolchain.toml` format. The goal here is
to make mach builds more similar to non-mach builds.

- The new format allows listing the required components, removing some of
  the complexity from our mach scripts.
- This means we must raise the required version of rustup to 1.23. The
  current version is 1.26.
- We no longer wrap every call to cargo and rustc in "rustup run" calls
  as both cargo and rustc will take care of installing and using all
  necessary components specified in `rust-toolchain.toml` when run
  inside the project directory.

1 files changed, 2 insertions, 4 deletions

diff --git a/python/servo/post_build_commands.py b/python/servo/post_build_commands.py
index a5d76134c4f..a9944775dda 100644
--- a/python/servo/post_build_commands.py
+++ b/python/servo/post_build_commands.py
@@ -244,10 +244,8 @@ class PostBuildCommands(CommandBase):
         help="Command-line arguments to be passed through to cargo doc")
     @CommandBase.build_like_command_arguments
     def doc(self, params: List[str], **kwargs):
-        self.ensure_bootstrapped(rustup_components=["rust-docs"])
-        rustc_path = check_output(
-            ["rustup" + BIN_SUFFIX, "which", "--toolchain", self.rust_toolchain(), "rustc"]
-        ).decode('utf-8')
+        self.ensure_bootstrapped()
+        rustc_path = check_output(["rustup" + BIN_SUFFIX, "which", "rustc"], cwd=self.context.topdir)
         assert path.basename(path.dirname(rustc_path)) == "bin"
         toolchain_path = path.dirname(path.dirname(rustc_path))
         rust_docs = path.join(toolchain_path, "share", "doc", "rust", "html")