Two CI fixes: Windows line-endings in manifest file, and "meta deterministic check".

- The Windows line-ending canonicalization was incomplete: we need to
  canonicalize the manifest text itself too!

- The "meta deterministic check" runs the cranelift-codegen build script
  N times outside of the source tree, examining what it produces to
  ensure the output is always the same (is detministic). This works fine
  when everything comes from the internal DSL, but when reading ISLE,
  this breaks because we no longer have the ISLE source paths.

  The initial ISLE integration did not hit this because without the
  `rebuild-isle` feature, it simply did nothing in the build script;
  now, with the manifest check, we hit the issue.

  The fix for now is just to turn off all ISLE-specific behavior in the
  build script by setting a special-purpose Cargo feature in the
  specific CI job. Eventually IMHO we should remove or find a better way
  to do this check.

cranelift/codegen/Cargo.toml

@@ -104,6 +104,10 @@ souper-harvest = ["souper-ir", "souper-ir/stringify"]
 # Recompile ISLE DSL source files into their generated Rust code.
 rebuild-isle = ["isle", "cranelift-codegen-meta/rebuild-isle"]
 
+# A hack to skip the ISLE-rebuild logic when testing for determinism
+# with the "Meta deterministic check" CI job.
+completely-skip-isle-for-ci-deterministic-check = []
+
 [badges]
 maintenance = { status = "experimental" }