Update msvcrt_name

This commit updates msvcrt_name to return the value of RUBY_SO_NAME or
ucrtbase.

Change taken from enkessler#182.

lib/childprocess/windows.rb

@@ -12,20 +12,12 @@ module Lib
       extend FFI::Library
 
       def self.msvcrt_name
-        host_part = RbConfig::CONFIG['host_os'].split("_")[1]
-        manifest  = File.join(RbConfig::CONFIG['bindir'], 'ruby.exe.manifest')
-
-        if host_part && host_part.to_i > 80 && File.exists?(manifest)
-          "msvcr#{host_part}"
-        else
-          "msvcrt"
-        end
+        RbConfig::CONFIG['RUBY_SO_NAME'][/msvc\w+/] || 'ucrtbase'
       end
 
       ffi_lib "kernel32", msvcrt_name
       ffi_convention :stdcall
 
-
     end # Library
   end # Windows
 end # ChildProcess