scotch: Depend on MPIDependency

Closes Homebrew#13241.

Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>

Library/Formula/scotch.rb

@@ -6,12 +6,22 @@ class Scotch < Formula
   version '5.1.12'
   md5 'f873ff2bad519f9be7bc7b117bbe0bc4'
 
+  depends_on MPIDependency.new(:cc)
+
   def install
     cd 'src' do
       ln_s 'Make.inc/Makefile.inc.i686_mac_darwin8', 'Makefile.inc'
-      system 'make scotch'
-      system 'make ptscotch'
-      system "make", "install", "prefix=#{prefix}"
+
+      # Use mpicc to compile everything
+      inreplace 'Makefile.inc' do |s|
+        s.change_make_var! 'CCS', ENV['MPICC']
+        s.change_make_var! 'CCP', ENV['MPICC']
+        s.change_make_var! 'CCD', ENV['MPICC']
+      end
+
+      system 'make', 'scotch'
+      system 'make', 'ptscotch'
+      system 'make', 'install', "prefix=#{prefix}"
     end
   end
 end