Auto merge of #9584 - henrifrancois:master, r=Eh2406

Handle "jobs = 0" case in cargo config files

Cargo hangs without output if the jobs argument under build in a cargo/config file is set to 0. This PR handles this case by providing an appropriate error.

Closes #9219

src/cargo/core/compiler/build_config.rs

@@ -68,7 +68,11 @@ impl BuildConfig {
                  its environment, ignoring the `-j` parameter",
             )?;
         }
-        let jobs = jobs.or(cfg.jobs).unwrap_or(::num_cpus::get() as u32);
+        let jobs = match jobs.or(cfg.jobs) {
+            None => ::num_cpus::get() as u32,
+            Some(j) if j != 0 => (::num_cpus::get() as u32).max(j),
+            Some(_) => anyhow::bail!("jobs may not be 0"),
+        };
 
         Ok(BuildConfig {
             requested_kinds,

tests/testsuite/build.rs

@@ -4802,6 +4802,24 @@ fn good_cargo_config_jobs() {
     p.cargo("build -v").run();
 }
 
+#[cargo_test]
+fn invalid_cargo_config_jobs() {
+    let p = project()
+        .file("src/lib.rs", "")
+        .file(
+            ".cargo/config",
+            r#"
+                [build]
+                jobs = 0
+            "#,
+        )
+        .build();
+    p.cargo("build -v")
+        .with_status(101)
+        .with_stderr_contains("error: jobs may not be 0")
+        .run();
+}
+
 #[cargo_test]
 fn invalid_jobs() {
     let p = project()