Allow FreeBSD to correctly detect number of CPUs

Use the same scheme as Darwin - sysctl instead of nproc, which doesn't exist in FreeBSD

Closes #2545
Co-authored-by: Daniel Bye <dbye@users.noreply.github.com>

plugins/bundler/bundler.plugin.zsh

@@ -57,7 +57,7 @@ bundle_install() {
   if _bundler-installed && _within-bundled-project; then
     local bundler_version=`bundle version | cut -d' ' -f3`
     if [[ $bundler_version > '1.4.0' || $bundler_version = '1.4.0' ]]; then
-      if [[ "$OSTYPE" = darwin* ]]
+      if [[ "$OSTYPE" = (darwin|freebsd)* ]]
       then
         local cores_num="$(sysctl -n hw.ncpu)"
       else