mpich2: only build static to fix ld seg fault

On Mountain Lion at least, ld keeps doing a sefault 11 during
the final link phase independent of whether superenv is used.
Mpich2 will build without problems when we

- Remove the `--enable-shared`

Fixes Homebrew/homebrew#15533

Closes Homebrew/homebrew#15544.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/mpich2.rb

@@ -29,9 +29,10 @@ class Mpich2 < Formula
     end
 
     args = [
+      "--disable-dependency-tracking",
+      "--disable-silent-rules",
       "--prefix=#{prefix}",
-      "--mandir=#{man}",
-      "--enable-shared"
+      "--mandir=#{man}"
     ]
     if ARGV.include? '--disable-fortran'
       args << "--disable-f77" << "--disable-fc"