Prabin,

Conf/tools_def.txt is the local untracked by git copy of the file that the build actually uses. The Conf/tools_def.txt does NOT get overwritten by the BaseTools/Conf/tools_def.template if it exists. So you can edit Conf/tools_def.txt  locally for an experiment. If you change  BaseTools/Conf/tools_def.template then people need to force the update via `. edksetup.sh —reconfig`, if they have a local copy. 

Thanks,

Andrew Fish

> On Oct 21, 2020, at 7:39 AM, Prabin CA <prabin.ca@arm.com> wrote:
> 
> Hi Andrew,
> 
> Yes, it copy from  BaseTools/Conf/tools_def.template to Conf/tools_def.txt, so if we make any changes in Conf/tools_def.txt will be over write by BaseTools/Conf/tools_def.template, then why we have to edit txt file instead template. Please confirm we have to edit template file or txt file. and we are made changes such as setting target and appending LDFLAGS on template file.
>