validator.rb: Print xcodebuild command on -v.

Proposed in https://github.com/CocoaPods/Specs/pull/9179.
Merge pull request #1883 from modocache/print-xcodebuild-command

validator.rb: Print xcodebuild command on -v.
validator.rb: Conform to 2-space indentation.
pod_target_installer: Remove 6-month-old comment.
Merge pull request #1885 from modocache/tiny-style-changes

Tiny style changes.
Ensure file descriptors are closed
Convert indention into spaces instead of tabs
Merge pull request #1900 from pietbrauer/fix_whitespace_in_target_installer_specs

Convert indention into spaces instead of tabs