Check MJIT support in one place

to fix test failure on trunk-no-mjit
https://gist.github.com/ko1/32ab982ffd7555988818773c08f97123

test/lib/jit_support.rb

@@ -47,7 +47,7 @@ module JITSupport
     return @supported if defined?(@supported)
     @supported = UNSUPPORTED_COMPILERS.all? do |regexp|
       !regexp.match?(RbConfig::CONFIG['CC'])
-    end
+    end && RbConfig::CONFIG["MJIT_SUPPORT"] != 'no'
   end
 
   def remove_mjit_logs(stderr)

test/ruby/test_jit.rb

@@ -3,8 +3,6 @@ require 'test/unit'
 require 'tmpdir'
 require_relative '../lib/jit_support'
 
-return if RbConfig::CONFIG["MJIT_SUPPORT"] == 'no'
-
 # Test for --jit option
 class TestJIT < Test::Unit::TestCase
   include JITSupport