print command before running

[milahu]

be more verbose on errors

 deno task build
 Warning deno task is unstable and may drastically change in the future
 Task build deno run -A --unstable script/build.ts
+Running "pkg-config --cflags --libs gtk+-3.0 webkit2gtk-4.0"
 error: Uncaught (in promise) NotFound: No such file or directory (os error 2)
   const result = await Deno.spawn(cmd, opts);
                             ^
     at spawnChild (deno:runtime/js/40_spawn.js:36:23)
     at Object.spawn (deno:runtime/js/40_spawn.js:231:12)
     at spawn (file:///tmp/tmp.aGowOqCn9e/vscode/vscode-deno/webview_deno/script/build.ts:43:29)
     at file:///tmp/tmp.aGowOqCn9e/vscode/vscode-deno/webview_deno/script/build.ts:131:30

the No such file error is not helpful