Fix new ruby OS X dep on libgmp.10.dylib

tools/distrib/build_ruby_environment_macos.sh

@@ -23,9 +23,9 @@ curl https://raw.githubusercontent.com/rake-compiler/rake-compiler/v1.0.3/tasks/
 
 # See https://github.com/grpc/grpc/issues/12161 for verconf.h patch details
 patch "$CROSS_RUBY" << EOF
---- cross-ruby.rake 2017-09-27 16:46:00.311020325 +0200
-+++ patched 2017-09-27 16:49:46.127016895 +0200
-@@ -133,7 +133,8 @@
+--- cross-ruby.rake	2018-04-10 11:32:16.000000000 -0700
++++ patched	2018-04-10 11:40:25.000000000 -0700
+@@ -133,8 +133,10 @@
      "--host=#{MINGW_HOST}",
      "--target=#{MINGW_TARGET}",
      "--build=#{RUBY_BUILD}",
@@ -33,9 +33,11 @@ patch "$CROSS_RUBY" << EOF
 +    '--enable-static',
 +    '--disable-shared',
      '--disable-install-doc',
++    '--without-gmp',
      '--with-ext='
    ]
-@@ -151,6 +152,7 @@
+ 
+@@ -151,6 +153,7 @@
  # make
  file "#{USER_HOME}/builds/#{MINGW_HOST}/#{RUBY_CC_VERSION}/ruby.exe" => ["#{USER_HOME}/builds/#{MINGW_HOST}/#{RUBY_CC_VERSION}/Makefile"] do |t|
    chdir File.dirname(t.prerequisites.first) do