Fix Homebrew build

Author: splhack

src/auto/configure

@@ -7233,6 +7233,12 @@ $as_echo "$rubyhdrdir" >&6; }
         rubyarchdir=`$vi_cv_path_ruby -r rbconfig -e "print ($ruby_rbconfig::CONFIG.has_key? 'rubyarchhdrdir') ? $ruby_rbconfig::CONFIG['rubyarchhdrdir'] : '$rubyhdrdir/'+$ruby_rbconfig::CONFIG['arch']"`
         if test -d "$rubyarchdir"; then
           RUBY_CFLAGS="$RUBY_CFLAGS -I$rubyarchdir"
+        else
+	  dnl rbconfig says darwin15 but 10.12 SDK has darwin16
+          rubyarchdir=${rubyarchdir/darwin15/darwin16}
+          if test -d "$rubyarchdir"; then
+            RUBY_CFLAGS="$RUBY_CFLAGS -I$rubyarchdir"
+          fi
         fi
         rubyversion=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig::CONFIG['ruby_version'].gsub(/\./, '')[0,2]"`
 	if test "X$rubyversion" = "X"; then

src/configure.ac

@@ -1904,6 +1904,12 @@ if test "$enable_rubyinterp" = "yes" -o "$enable_rubyinterp" = "dynamic"; then
         rubyarchdir=`$vi_cv_path_ruby -r rbconfig -e "print ($ruby_rbconfig::CONFIG.has_key? 'rubyarchhdrdir') ? $ruby_rbconfig::CONFIG[['rubyarchhdrdir']] : '$rubyhdrdir/'+$ruby_rbconfig::CONFIG[['arch']]"`
         if test -d "$rubyarchdir"; then
           RUBY_CFLAGS="$RUBY_CFLAGS -I$rubyarchdir"
+        else
+	  dnl rbconfig says darwin15 but 10.12 SDK has darwin16
+          rubyarchdir=${rubyarchdir/darwin15/darwin16}
+          if test -d "$rubyarchdir"; then
+            RUBY_CFLAGS="$RUBY_CFLAGS -I$rubyarchdir"
+          fi
         fi
         rubyversion=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig::CONFIG[['ruby_version']].gsub(/\./, '')[[0,2]]"`
 	if test "X$rubyversion" = "X"; then