Auto merge of rust-lang#125732 - matthiaskrgr:rollup-bozbtk3, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#124655 (Add `-Zfixed-x18`)
 - rust-lang#125693 (Format all source files in `tests/coverage/`)
 - rust-lang#125700 (coverage: Avoid overflow when the MC/DC condition limit is exceeded)
 - rust-lang#125705 (Reintroduce name resolution check for trying to access locals from an inline const)
 - rust-lang#125708 (tier 3 target policy: clarify the point about producing assembly)
 - rust-lang#125715 (remove unneeded extern crate in rmake test)
 - rust-lang#125719 (Extract coverage-specific code out of `compiletest::runtest`)

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

Author: bors

compiler/rustc_codegen_llvm/messages.ftl

@@ -18,6 +18,8 @@ codegen_llvm_error_creating_import_library =
 codegen_llvm_error_writing_def_file =
     Error writing .DEF file: {$error}
 
+codegen_llvm_fixed_x18_invalid_arch = the `-Zfixed-x18` flag is not supported on the `{$arch}` architecture
+
 codegen_llvm_from_llvm_diag = {$message}
 
 codegen_llvm_from_llvm_optimization_diag = {$filename}:{$line}:{$column} {$pass_name} ({$kind}): {$message}

compiler/rustc_codegen_llvm/src/errors.rs

@@ -254,3 +254,9 @@ pub struct MismatchedDataLayout<'a> {
 pub(crate) struct InvalidTargetFeaturePrefix<'a> {
     pub feature: &'a str,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_llvm_fixed_x18_invalid_arch)]
+pub(crate) struct FixedX18InvalidArch<'a> {
+    pub arch: &'a str,
+}