[ruby/prism] Turn off LibrarySymbolsTest on powerpc64le

https://github.com/ruby/prism/commit/6e432f3de5

test/prism/library_symbols_test.rb

@@ -4,6 +4,9 @@ require_relative "test_helper"
 
 return if RUBY_PLATFORM !~ /linux/
 
+# TODO: determine why these symbols are incorrect on ppc64le
+return if RUBY_PLATFORM =~ /powerpc64le/
+
 module Prism
   #
   #  examine a prism dll or static archive for expected external symbols.