Fix strict typecheck errors.

Library/Homebrew/extend/os/linux/cleaner.rb

@@ -4,6 +4,8 @@
 class Cleaner
   private
 
+  extend T::Sig
+  sig { params(path: Pathname).returns(T.nilable(T::Boolean)) }
   def executable_path?(path)
     path.elf? || path.text_executable?
   end

Library/Homebrew/extend/os/linux/formula_cellar_checks.rb

@@ -2,6 +2,8 @@
 # frozen_string_literal: true
 
 module FormulaCellarChecks
+  extend T::Sig
+  sig { params(filename: Pathname).returns(T::Boolean) }
   def valid_library_extension?(filename)
     generic_valid_library_extension?(filename) || filename.basename.to_s.include?(".so.")
   end

Library/Homebrew/extend/os/linux/software_spec.rb

@@ -2,6 +2,8 @@
 # frozen_string_literal: true
 
 class BottleSpecification
+  extend T::Sig
+  sig { returns(T::Boolean) }
   def skip_relocation?
     false
   end

Library/Homebrew/extend/os/linux/utils/analytics.rb

@@ -4,12 +4,15 @@
 module Utils
   module Analytics
     class << self
+      extend T::Sig
+      sig { returns(String) }
       def formula_path
         return generic_formula_path if Homebrew::EnvConfig.force_homebrew_on_linux?
 
         "formula-linux"
       end
 
+      sig { returns(String) }
       def analytics_path
         return generic_analytics_path if Homebrew::EnvConfig.force_homebrew_on_linux?
 

Library/Homebrew/extend/os/mac/formula_support.rb

@@ -2,6 +2,8 @@
 # frozen_string_literal: true
 
 class KegOnlyReason
+  extend T::Sig
+  sig { returns(T::Boolean) }
   def applicable?
     true
   end

Library/Homebrew/extend/os/mac/hardware.rb

@@ -2,6 +2,8 @@
 # frozen_string_literal: true
 
 module Hardware
+  extend T::Sig
+  sig { params(version: T.nilable(Version)).returns(Symbol) }
   def self.oldest_cpu(version = MacOS.version)
     if CPU.arch == :arm64
       :arm_vortex_tempest

Library/Homebrew/extend/os/mac/missing_formula.rb

@@ -8,7 +8,10 @@ require "cask/caskroom"
 
 module Homebrew
   module MissingFormula
+    extend T::Sig
     class << self
+      extend T::Sig
+      sig { params(name: String).returns(T.nilable(String)) }
       def disallowed_reason(name)
         case name.downcase
         when "xcode"
@@ -33,12 +36,14 @@ module Homebrew
         end
       end
 
+      sig { params(name: String, silent: T::Boolean, show_info: T::Boolean).returns(T.nilable(String)) }
       def cask_reason(name, silent: false, show_info: false)
         return if silent
 
         suggest_command(name, show_info ? "info" : "install")
       end
 
+      sig { params(name: String, command: String).returns(T.nilable(String)) }
       def suggest_command(name, command)
         suggestion = <<~EOS
           Found a cask named "#{name}" instead. Try

Library/Homebrew/extend/os/mac/utils/analytics.rb

@@ -4,6 +4,8 @@
 module Utils
   module Analytics
     class << self
+      extend T::Sig
+      sig { returns(String) }
       def custom_prefix_label
         "non-/usr/local"
       end