formula_installer: default_formula using build.

Use the build options instead of whether the requirement is optional to
work out if it is needed. This handles the case of an optional
requirement becoming needed because it's a dependency for another
formula.

Closes Homebrew/homebrew#31476.

Library/Homebrew/formula_installer.rb

@@ -239,9 +239,9 @@ class FormulaInstaller
     raise UnsatisfiedRequirements.new(f, fatals) unless fatals.empty?
   end
 
-  def install_requirement_default_formula?(req)
+  def install_requirement_default_formula?(req, build)
     return false unless req.default_formula?
-    return false if req.optional?
+    return false if build.without?(req)
     return true unless req.satisfied?
     pour_bottle? || build_bottle?
   end
@@ -262,7 +262,7 @@ class FormulaInstaller
           Requirement.prune
         elsif req.build? && dependent != f && install_bottle_for_dep?(dependent, build)
           Requirement.prune
-        elsif install_requirement_default_formula?(req)
+        elsif install_requirement_default_formula?(req, build)
           dep = req.to_dependency
           deps.unshift(dep)
           formulae.unshift(dep.to_formula)