Auto merge of #13128 - Veykril:invocation-strategy, r=Veykril

Implement invocation strategy config

Fixes https://github.com/rust-lang/rust-analyzer/issues/10793

This allows to change how we run build scripts (and `checkOnSave`), exposing two configs:
- `once`: run the specified command once in the project root (the working dir of the server)
- `per_workspace`: run the specified command per workspace in the corresponding workspace

This also applies to `checkOnSave` likewise, though `once_in_root` is useless there currently, due to https://github.com/rust-lang/cargo/issues/11007

crates/project-model/src/lib.rs

@@ -157,3 +157,10 @@ fn utf8_stdout(mut cmd: Command) -> Result<String> {
     let stdout = String::from_utf8(output.stdout)?;
     Ok(stdout.trim().to_string())
 }
+
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
+pub enum InvocationStrategy {
+    Once,
+    #[default]
+    PerWorkspace,
+}