Bug 1900489 - Remove dist.missing-tools option from config.toml when building rust compiler. r=firefox-build-system-reviewers,sergesanspaille

Building rustfmt would fail regularly, so the option was added to ignore
the problem, but that presumably hasn't been the case in a while.

The option was removed in rustc 1.80.

Differential Revision: https://phabricator.services.mozilla.com/D212491

taskcluster/scripts/misc/repack_rust.py

@@ -412,11 +412,6 @@ def build_src(install_dir, host, targets, patches):
     # `sysconfdir` is overloaded to be relative instead of absolute.
     # This is the default of `install.sh`, but for whatever reason
     # `x.py install` has its own default of `/etc` which we don't want.
-    #
-    # `missing-tools` is set so `rustfmt` is allowed to fail. This means
-    # we can "succeed" at building Rust while failing to build, say, Cargo.
-    # Ideally the build system would have better granularity:
-    # https://github.com/rust-lang/rust/issues/79249
     base_config = textwrap.dedent(
         """
         [build]
@@ -435,9 +430,6 @@ def build_src(install_dir, host, targets, patches):
         prefix = "{prefix}"
         sysconfdir = "etc"
 
-        [dist]
-        missing-tools = true
-
         [llvm]
         download-ci-llvm = false
         """.format(