Disable CMake bootstrap by default (#7089)

It sounds as if we shouldn't need this anymore.

Author: neonichu

Utilities/bootstrap

@@ -131,6 +131,7 @@ def add_build_args(parser):
     parser.add_argument(
         "--skip-cmake-bootstrap",
         action="store_true",
+        default=True,
         help="build with prebuilt package manager in toolchain if it exists")
     parser.add_argument(
         "--libswiftpm-install-dir",