Added support for clean target to remove gcluster binary and the ghpc…

[nadig-google]

This CL updates the Makefile to add a "clean" make target. Running "make clean" will remove the regular file "gcluster" and the symlink "ghpc" (links to gcluster).

This PR to removes the build targets from the following directories after checking if the files exist and if it has permissions to delete them:

• current dir
• ~/bin
• /usr/local/bin

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[nadig-google]

Added label

[abbas1902]

LGTM