Try USE_OPENSOURCE_TEST_TOOL=yes (#13566)

ya.conf

@@ -24,6 +24,7 @@ use_command_file_in_testtool = true
 
 [host_platform_flags]
 OPENSOURCE = "yes"
+USE_OPENSOURCE_TEST_TOOL = "yes"
 USE_PREBUILT_TOOLS = "no"
 APPLE_SDK_LOCAL = "yes"
 USE_CLANG_CL = "yes"