bootstrap: Ignore rust.debuginfo-level-tests for codegen tests

codegen tests typically depend on the raw LLVM IR output and are
sensitive to debuginfo level. So do not apply
`rust.debuginfo-level-tests` for codegen tests.

Before this commit:

    $ ./x test --set rust.debuginfo-level-tests=2 tests/codegen --force-rerun
    test result: FAILED. 654 passed; 136 failed; 75 ignored; 0 measured; 0 filtered out; finished in 3.22s

After this commit:

    $ ./x test --set rust.debuginfo-level-tests=2 tests/codegen --force-rerun
    NOTE: ignoring `rust.debuginfo-level-tests=2` for codegen tests
    test result: ok. 790 passed; 0 failed; 75 ignored; 0 measured; 0 filtered out; finished in 3.21s

Author: Enselic

src/bootstrap/src/core/build_steps/test.rs

@@ -1810,7 +1810,24 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
         }
 
         let mut flags = if is_rustdoc { Vec::new() } else { vec!["-Crpath".to_string()] };
-        flags.push(format!("-Cdebuginfo={}", builder.config.rust_debuginfo_level_tests));
+        flags.push(format!(
+            "-Cdebuginfo={}",
+            if suite == "codegen" {
+                // codegen tests typically check LLVM IR and are sensitive to additional debuginfo.
+                // So do not apply `rust.debuginfo-level-tests` for codegen tests.
+                if builder.config.rust_debuginfo_level_tests
+                    != crate::core::config::DebuginfoLevel::None
+                {
+                    println!(
+                        "NOTE: ignoring `rust.debuginfo-level-tests={}` for codegen tests",
+                        builder.config.rust_debuginfo_level_tests
+                    );
+                }
+                crate::core::config::DebuginfoLevel::None
+            } else {
+                builder.config.rust_debuginfo_level_tests
+            }
+        ));
         flags.extend(builder.config.cmd.compiletest_rustc_args().iter().map(|s| s.to_string()));
 
         if suite != "mir-opt" {