Align our subprocess usage with current best practices. (#12940)

* Align our subprocess usage with current best practices.

* remove unused import

* Apply suggestions from code review

Co-authored-by: Ryan <fauxpark@gmail.com>

* fix the cpp invocation for older python

* allow for unprompted installation

* make sure qmk new-keyboard works on windows

Co-authored-by: Ryan <fauxpark@gmail.com>

util/install/freebsd.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 _qmk_install_prepare() {
-    sudo pkg update
+    sudo pkg update $SKIP_PROMPT
 }
 
 _qmk_install() {