Only handle build-errors when it's a build-error

Refs Homebrew/homebrew#15164.

Library/Homebrew/cmd/--config.rb

@@ -112,6 +112,13 @@ module Homebrew extend self
     puts "X11: #{describe_x11}"
   end
 
+  def write_build_config f
+    $f = f
+    def Homebrew.puts(*foo); $f.puts(*foo); end
+    Homebrew.dump_build_config
+    class << Homebrew; undef :puts; end
+  end
+
   def dump_verbose_config
     puts "HOMEBREW_VERSION: #{HOMEBREW_VERSION}"
     puts "HEAD: #{head}"

Library/Homebrew/formula.rb

@@ -542,29 +542,24 @@ protected
       f.write(rd.read) until rd.eof?
 
       Process.wait
-      raise unless $?.success?
+
+      unless $?.success?
+        unless ARGV.verbose?
+          f.flush
+          Kernel.system "/usr/bin/tail -n 5 #{logfn}"
+        end
+        f.puts
+        require 'cmd/--config'
+        Homebrew.write_build_config(f)
+        raise BuildError.new(self, cmd, args, $?)
+      end
     end
 
-    removed_ENV_variables.each do |key, value|
-      ENV[key] = value # ENV.kind_of? Hash  # => false
-    end if removed_ENV_variables
-
-  rescue
-    if f
-      f.flush
-      Kernel.system "/usr/bin/tail -n 5 #{logfn}" unless ARGV.verbose?
-      require 'cmd/--config'
-      $f = f
-      def Homebrew.puts(*foo); $f.puts *foo end
-      f.puts
-      Homebrew.dump_build_config
-      class << Homebrew; undef :puts end
-    else
-      puts "No logs recorded :(" unless ARGV.verbose?
-    end
-    raise BuildError.new(self, cmd, args, $?)
   ensure
     f.close if f
+    removed_ENV_variables.each do |key, value|
+      ENV[key] = value
+    end if removed_ENV_variables
   end
 
 public