Use toolchain install instead of multiple commands

lib/main.js

@@ -32,14 +32,11 @@ function run() {
                 .filter((target) => target.length > 0);
             if (version) {
                 yield rustup.install();
+                yield exec.exec('rustup', ['toolchain', 'install', version,
+                    ...(components.length > 0 ? ['-c', ...components] : []),
+                    ...(targets.length > 0 ? ['-t', ...targets] : []),
+                ]);
                 yield exec.exec('rustup', ['default', version]);
-                yield exec.exec('rustup', ['update', version]);
-                for (let component of components) {
-                    yield exec.exec('rustup', ['component', 'add', component]);
-                }
-                for (let target of targets) {
-                    yield exec.exec('rustup', ['target', 'add', target]);
-                }
             }
         }
         catch (error) {

lib/rustup.js

@@ -30,6 +30,11 @@ function install() {
             core.debug('rustup is located under: ' + toolPath);
             core.addPath(path.join(toolPath, 'bin'));
         }
+        else {
+            // update the GitHub managed VM version of rustup
+            // to leverage newer features like "latest latest compatible nightly"
+            yield exec.exec('rustup', ['self', 'update']);
+        }
     });
 }
 exports.install = install;