Warn on bottles skipped due to non-default Cellar.

Closes Homebrew/homebrew#18333.

Library/Homebrew/bottles.rb

@@ -9,7 +9,7 @@ def bottle_filename f, bottle_revision=nil
   "#{name}-#{version}#{bottle_native_suffix(bottle_revision)}"
 end
 
-def install_bottle? f
+def install_bottle? f, warn=false
   return true if f.downloader and defined? f.downloader.local_bottle_path \
     and f.downloader.local_bottle_path
 
@@ -17,7 +17,10 @@ def install_bottle? f
   return false unless f.pour_bottle?
   return false unless f.build.used_options.empty?
   return false unless bottle_current?(f)
-  return false if f.bottle.cellar != :any && f.bottle.cellar != HOMEBREW_CELLAR.to_s
+  if f.bottle.cellar != :any && f.bottle.cellar != HOMEBREW_CELLAR.to_s
+    opoo "Building source; cellar of #{f}'s bottle is #{f.bottle.cellar}" if warn
+    return false
+  end
 
   true
 end

Library/Homebrew/formula_installer.rb

@@ -25,7 +25,7 @@ class FormulaInstaller
   end
 
   def pour_bottle?
-    install_bottle?(f) && (tab.used_options.empty? rescue true) && options.empty?
+    (tab.used_options.empty? rescue true) && options.empty? && install_bottle?(f, true)
   end
 
   def check_install_sanity