install: prune build-only deps of deps

This avoids needlessly installing build-time dependencies of dependencies
which are not themselves being built from source.

Library/Homebrew/formula_installer.rb

@@ -114,7 +114,7 @@ class FormulaInstaller
 
   def install_bottle_for?(dep, build)
     return pour_bottle? if dep == formula
-    return false if build_from_source?
+    return false if ARGV.build_formula_from_source?(dep)
     return false unless dep.bottle && dep.pour_bottle?
     return false unless build.used_options.empty?
     return false unless dep.bottle.compatible_cellar?