makefile: Don't fail while building and installing multiple versions

When older version is already built and later code is updated to newer version and built multiple .whl files are present in dist/ directory. This confuses the install script that assumes only one .whl is present. Pip refuses to install multiple versions of the same package. This error was seen when bringing up the 'stable' container.

Signed-off-by: Sunil Mohan Adapa sunil@medhas.org