Only rescue realpath calls during require on Solaris

Remove temporary skip of test_no_curdir to see if this fixes the
problem.

load.c

@@ -1060,7 +1060,7 @@ rb_ext_ractor_safe(bool flag)
     GET_THREAD()->ext_config.ractor_safe = flag;
 }
 
-#if 1
+#ifdef __sun
 static VALUE
 required_feature__realpath(VALUE path)
 {

test/ruby/test_process.rb

@@ -1732,9 +1732,6 @@ class TestProcess < Test::Unit::TestCase
   end
 
   def test_no_curdir
-    if /solaris/i =~ RUBY_PLATFORM
-      skip "Temporary skip to avoid CI failures after commit to use realpath on required files"
-    end
     with_tmpchdir {|d|
       Dir.mkdir("vd")
       status = nil