postprocessor: add expand tag
postprocessor: add expand tag

this tag doesn't relativize path strings but it does expand env
vars in strings

	Exports map[string]string `move:"installs" build:"expand"`

add this tag to variables in targets that you want envinroment
variables expanded in.

Signed-off-by: Sevki <a0f1490a20d0211c997b44bc357e1972deab8ae3@sevki.org>

bldy/build,bldy/build,bldy/build,bldy/build