Ignore buggy clippy::lint_groups_priority lint

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
    --> Cargo.toml:35:1
     |
  35 | rust_2018_idioms = "warn"
     | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
  36 | single_use_lifetimes = "warn"
     | -------------------- has the same priority as this lint
     |
     = note: the order of the lints in the table is ignored by Cargo
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
     = note: `#[deny(clippy::lint_groups_priority)]` on by default
  help: to have lints override the group set `rust_2018_idioms` to a lower priority
     |
  35 | rust_2018_idioms = { level = "warn", priority = -1 }
     |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

tests/avr/Cargo.toml

@@ -24,6 +24,8 @@ resolver = "2"
 rust_2018_idioms = "warn"
 single_use_lifetimes = "warn"
 # unsafe_op_in_unsafe_fn = "warn" # Set at crate-level instead since https://github.com/rust-lang/rust/pull/100081 is not available on MSRV
+[lints.clippy]
+lint_groups_priority = { level = "allow", priority = 1 } # clippy bug: https://github.com/rust-lang/rust-clippy/issues/12270
 
 [profile.dev]
 lto = true

tests/gba/Cargo.toml

@@ -18,6 +18,8 @@ resolver = "2"
 rust_2018_idioms = "warn"
 single_use_lifetimes = "warn"
 # unsafe_op_in_unsafe_fn = "warn" # Set at crate-level instead since https://github.com/rust-lang/rust/pull/100081 is not available on MSRV
+[lints.clippy]
+lint_groups_priority = { level = "allow", priority = 1 } # clippy bug: https://github.com/rust-lang/rust-clippy/issues/12270
 
 [profile.dev]
 # TODO: "GBA: Illegal opcode: e7ffdefe" on opt-level=0, GBA hang on opt-level={1,s,z}

tests/no-std-qemu/Cargo.toml

@@ -35,6 +35,9 @@ resolver = "2"
 rust_2018_idioms = "warn"
 single_use_lifetimes = "warn"
 # unsafe_op_in_unsafe_fn = "warn" # Set at crate-level instead since https://github.com/rust-lang/rust/pull/100081 is not available on MSRV
+[lints.clippy]
+lint_groups_priority = { level = "allow", priority = 1 } # clippy bug: https://github.com/rust-lang/rust-clippy/issues/12270
+single_match = { level = "allow", priority = 1 }
 
 [profile.dev]
 opt-level = "s"

tests/xtensa/Cargo.toml

@@ -22,6 +22,8 @@ resolver = "2"
 rust_2018_idioms = "warn"
 single_use_lifetimes = "warn"
 # unsafe_op_in_unsafe_fn = "warn" # Set at crate-level instead since https://github.com/rust-lang/rust/pull/100081 is not available on MSRV
+[lints.clippy]
+lint_groups_priority = { level = "allow", priority = 1 } # clippy bug: https://github.com/rust-lang/rust-clippy/issues/12270
 
 [profile.dev]
 opt-level = 'z'