…der-no-read-perms, r=isikkema

Fix -Zmeta-stats ICE by giving `FileEncoder` file read permissions

Fixes rust-lang#101001

As far as I can tell, rust-lang#101001 is caused because the file is being created with write-only permissions here: https://github.com/rust-lang/rust/blob/master/compiler/rustc_serialize/src/opaque.rs#L196

but it is trying to be read here: https://github.com/rust-lang/rust/blob/master/compiler/rustc_metadata/src/rmeta/encoder.rs#L780

This PR attempts to fix this by creating/opening the file with the same permissions as `File::create()` with the addition of read.

Rollup of 12 pull requests

Successful merges:

 - rust-lang#100250 (Manually cleanup token stream when macro expansion aborts.)
 - rust-lang#101014 (Fix -Zmeta-stats ICE by giving `FileEncoder` file read permissions)
 - rust-lang#101958 (Improve error for when query is unsupported by crate)
 - rust-lang#101976 (MirPhase: clarify that linting is not a semantic change)
 - rust-lang#102001 (Use LLVM C-API to build atomic cmpxchg and fence)
 - rust-lang#102008 (Add GUI test for notable traits element position)
 - rust-lang#102013 (Simplify rpitit handling on lower_fn_decl)
 - rust-lang#102021 (some post-valtree cleanup)
 - rust-lang#102027 (rustdoc: remove `docblock` class from `item-decl`)
 - rust-lang#102034 (rustdoc: remove no-op CSS `h1-6 { border-bottom-color }`)
 - rust-lang#102038 (Make the `normalize-overflow` rustdoc test actually do something)
 - rust-lang#102053 (:arrow_up: rust-analyzer)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup