Skip the entire Process.clock_getres spec on FreeBSD

* Clocks don't match the reported precision.
* https://rubyci.org/logs/rubyci.s3.amazonaws.com/freebsd11zfs/ruby-trunk/log/20190428T093003Z.fail.html.gz

spec/ruby/core/process/clock_getres_spec.rb

@@ -2,6 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/clocks'
 
 describe "Process.clock_getres" do
+  platform_is_not :freebsd do # clock_getres() seems incorrect on FreeBSD
     ProcessSpecs.clock_constants.each do |name, value|
       it "matches the clock in practice for Process::#{name}" do
         times = []
@@ -10,11 +11,9 @@ describe "Process.clock_getres" do
         end
         reported = Process.clock_getres(value, :nanosecond)
 
-      platform_is_not :bsd do
         # The clock should not be more accurate than reported (times should be
         # a multiple of reported precision.)
         times.select { |t| t % reported > 0 }.should be_empty
-      end
 
         # We're assuming precision is a multiple of ten - it may or may not
         # be an incompatibility if it isn't but we'd like to notice this,
@@ -28,6 +27,7 @@ describe "Process.clock_getres" do
         times.select { |t| t % (reported * 10) == 0  }.size.should_not == times.size
       end
     end
+  end
 
   # These are documented