use relative lib path instead of expanded path to avoid using mkmf

lib/rake/extensiontask.rb

@@ -161,15 +161,15 @@ def define_compile_tasks(for_platform = nil, ruby_ver = RUBY_VERSION)
       task "copy:#{@name}:#{platf}:#{ruby_ver}" => [lib_path, tmp_binary_path, "#{tmp_path}/Makefile"] do
         # install in lib for native platform only
         unless for_platform
-          expaned_lib_path = File.expand_path(lib_path)
+          relative_lib_path = Pathname(lib_path).relative_path_from(tmp_path)
 
-          make_command = "#{make}" \
-            " install" \
-            " sitearchdir=#{expaned_lib_path}" \
-            " sitelibdir=#{expaned_lib_path}" \
-            " target_prefix="
+          make_command_line = Shellwords.shellsplit(make)
+          make_command_line << "install"
+          make_command_line << "sitearchdir=#{relative_lib_path}"
+          make_command_line << "sitelibdir=#{relative_lib_path}"
+          make_command_line << "target_prefix="
 
-          sh(make_command, chdir: tmp_path)
+          sh(*make_command_line, chdir: tmp_path)
         end
       end
       # copy binary from temporary location to staging directory