sbcl: patch in support for parallel builds

Closes Homebrew/homebrew#37931.
Closes Homebrew/homebrew#36440.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Formula/sbcl.rb

@@ -54,6 +54,10 @@ class Sbcl < Formula
     sha1 "4d08e56e7e261db47ffdfef044149b001e6cd7c1"
   end
 
+  # Restore parallel build support.
+  # See: https://bugs.launchpad.net/sbcl/+bug/1434768
+  patch :DATA
+
   def write_features
     features = []
     features << ":sb-thread" if build.with? "threads"
@@ -105,3 +109,15 @@ class Sbcl < Formula
     assert_equal "4", output.strip
   end
 end
+__END__
+--- a/contrib/asdf/Makefile
++++ b/contrib/asdf/Makefile
+@@ -8,7 +8,7 @@ $(UIOP_FASL):: uiop.lisp ../../output/sbcl.core
+	mkdir -p $(DEST)
+	$(SBCL) --eval '(compile-file #p"SYS:CONTRIB;ASDF;UIOP.LISP" :output-file (parse-native-namestring "$@"))' </dev/null
+
+-$(ASDF_FASL):: asdf.lisp ../../output/sbcl.core
++$(ASDF_FASL):: asdf.lisp ../../output/sbcl.core $(UIOP_FASL)
+	if [ -d asdf-upstream ] ; then rm -rf asdf-upstream ; fi
+	mkdir -p $(DEST)
+	$(SBCL) --eval '(compile-file #p"SYS:CONTRIB;ASDF;ASDF.LISP" :output-file (parse-native-namestring "$@"))' </dev/null