Fix jt build to use the same JDK for mx graalvm-home

Author: eregon

tool/jt.rb

@@ -1895,7 +1895,7 @@ def build_graalvm(*options)
                *options]
 
     mx(*mx_args, 'build', java_home: java_home)
-    build_dir = mx(*mx_args, 'graalvm-home', capture: true).lines.last.chomp
+    build_dir = mx(*mx_args, 'graalvm-home', java_home: java_home, capture: true).lines.last.chomp
 
     dest = "#{TRUFFLERUBY_DIR}/mxbuild/graalvm"
     FileUtils.rm_rf dest