Swift: enable VSCode to build extractor via CMake

The `-arch=x86_64` from `swift/rules.bzl` turns out to be unnecessary,
even on Arm-based Macs.

.vscode/settings.json

@@ -1,3 +1,5 @@
 {
-    "omnisharp.autoStart": false
+  "omnisharp.autoStart": false,
+  "cmake.sourceDirectory": "${workspaceFolder}/swift",
+  "cmake.buildDirectory": "${workspaceFolder}/bazel-cmake-build"
 }