Auto merge of #122663 - beetrees:non-unicode-env-error, r=TaKO8Ki

Fix error message for `env!` when env var is not valid Unicode

Currently (without this PR) the `env!` macro emits an ```environment variable `name` not defined at compile time``` error when the environment variable is defined, but not a valid Unicode string. This PR introduces a separate more accurate error message, and a test to verify this behaviour.

For reference, before this PR, the new test would have outputted:
```
error: environment variable `NON_UNICODE_VAR` not defined at compile time
 --> non_unicode_env.rs:2:13
  |
2 |     let _ = env!("NON_UNICODE_VAR");
  |             ^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: use `std::env::var("NON_UNICODE_VAR")` to read the variable at run time
  = note: this error originates in the macro `env` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error
```

whereas with this PR, the test ouputs:
```
error: environment variable `NON_UNICODE_VAR` is not a valid Unicode string
 --> non_unicode_env.rs:2:13
  |
2 |     let _ = env!("NON_UNICODE_VAR");
  |             ^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the macro `env` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error
```

2 files changed, 23 insertions, 1 deletions

diff --git a/src/tools/run-make-support/src/lib.rs b/src/tools/run-make-support/src/lib.rs
index 7975677286d..48fa2bbf1ac 100644
--- a/src/tools/run-make-support/src/lib.rs
+++ b/src/tools/run-make-support/src/lib.rs
@@ -19,7 +19,11 @@ pub fn tmp_dir() -> PathBuf {
 }
 
 fn handle_failed_output(cmd: &str, output: Output, caller_line_number: u32) -> ! {
-    eprintln!("command failed at line {caller_line_number}");
+    if output.status.success() {
+        eprintln!("command incorrectly succeeded at line {caller_line_number}");
+    } else {
+        eprintln!("command failed at line {caller_line_number}");
+    }
     eprintln!("{cmd}");
     eprintln!("output status: `{}`", output.status);
     eprintln!("=== STDOUT ===\n{}\n\n", String::from_utf8(output.stdout).unwrap());
diff --git a/src/tools/run-make-support/src/rustc.rs b/src/tools/run-make-support/src/rustc.rs
index 1b358817a79..50ff0d26bbb 100644
--- a/src/tools/run-make-support/src/rustc.rs
+++ b/src/tools/run-make-support/src/rustc.rs
@@ -1,4 +1,5 @@
 use std::env;
+use std::ffi::OsStr;
 use std::path::Path;
 use std::process::{Command, Output};
 
@@ -133,6 +134,11 @@ impl Rustc {
         self
     }
 
+    pub fn env(&mut self, name: impl AsRef<OsStr>, value: impl AsRef<OsStr>) -> &mut Self {
+        self.cmd.env(name, value);
+        self
+    }
+
     // Command inspection, output and running helper methods
 
     /// Get the [`Output`][std::process::Output] of the finished `rustc` process.
@@ -153,6 +159,18 @@ impl Rustc {
         output
     }
 
+    #[track_caller]
+    pub fn run_fail(&mut self) -> Output {
+        let caller_location = std::panic::Location::caller();
+        let caller_line_number = caller_location.line();
+
+        let output = self.cmd.output().unwrap();
+        if output.status.success() {
+            handle_failed_output(&format!("{:#?}", self.cmd), output, caller_line_number);
+        }
+        output
+    }
+
     /// Inspect what the underlying [`Command`] is up to the current construction.
     pub fn inspect(&mut self, f: impl FnOnce(&Command)) -> &mut Self {
         f(&self.cmd);