The `build` script does nothing when called from outside it's directory

The build script does not find it's required files when we run the command from the target directory.

Steps to reproduce

1. create a project hierarchy to simulate multi-environments

   ~# mkdir -p /tmp/my-project/{prod,dev,staging}

2. move to that directory

   ~# cd /tmp/my-project/

3. get the tools utilities

   /tmp/my-project# git clone https://gitlab.mim-libre.fr/EOLE/eole-3/tools.git

4. configure the dev environment

   /tmp/my-project# cd /tmp/my-project/dev
   /tmp/my-project/dev# cp ../tools/vars.ini .

5. generate the base application deployment

   /tmp/my-project/dev# /tmp/my-project/tools/build -c /tmp/my-project/dev/vars.ini gen-socle
   Usage: build [OPTIONS] COMMAND [ARGS]...
   Try 'build --help' for help.
   
   Error: Invalid value for '-cc' / '--clusterconfigfile': Path 'cluster-vars.ini' does not exist.

6. configure the cluster-vars.ini for dev

   /tmp/my-project/dev# cp ../tools/cluster-vars.ini .
   /tmp/my-project/dev# /tmp/my-project/tools/build -c /tmp/my-project/dev/vars.ini gen-socle
   /tmp/my-project/dev#

Proposed solutions

I think the build script should search for it's files in it's own directory:

• the templates/ must be searched relatives to the build directory
• the vars.ini and cluster-vars.ini
  • may be kept the current way, when a user move in another directory, the tool will use the ones in the current directory
  • may be search in the build directory and users are forced to use --configfile and --clusterconfigfile