user- The most basic rule of GNU Make and the environment is that any variable set in the environment when GNU Make is started will be available as a GNU Make ma...The most basic rule of GNU Make and the environment is that any variable set in the environment when GNU Make is started will be available as a GNU Make macro inside the Makefile. For example, if FOO is set in the environment to foo when GNU Make is run then the following Makefile: $(warning $(FOO))
