platypus: fix --HEAD builds

Closes #27085.
Remove deprecation notice from system "xcodebuild"

The new xcodebuild method calls system "xcodebuild" underneath, so this
notice would always be printed. Instead we will just rely on the audit
check.

Fixes #27092.
Remove "brew info <URL>"

Closes #27076.
FormulaInstaller: verify dependencies map to formulae before locking
Add TapDependency
moc: use :optional dep
Use Dependency#option_name in BuildOptions#add_dep_option