feat: flag to limit the thread count used by LS

Ref: arduino/arduino-language-server#177
Signed-off-by: Akos Kitta <[email protected]>

Author: Akos Kitta

Diff for: src/ino.ts

@@ -55,6 +55,10 @@ export interface StartLanguageServerParams {
    * If `true`, the logging is not forwarded to the _Output_ view via the language client.
    */
   readonly silentOutput?: boolean;
+  /**
+   * Number of async workers used by `clangd`. Background index also uses this many workers. If `0`, `clangd` uses all available cores. It's `0` by default.
+   */
+  readonly jobs?: number;
 }
 
 /**
@@ -177,6 +181,7 @@ async function buildLanguageClient(
     flags,
     env,
     log,
+    jobs,
   } = config;
   const args = [
     '-clangd',
@@ -216,6 +221,10 @@ async function buildLanguageClient(
       args.push('-logpath', logPath);
     }
   }
+  // https://github.com/arduino/arduino-language-server/pull/177
+  if (jobs) {
+    args.push('-jobs', String(jobs));
+  }
   const clientOptions: LanguageClientOptions = {
     initializationOptions: {},
     documentSelector: ['ino', 'c', 'cpp', 'cc', 'cxx', 'h', 'hpp', 'pde'],