cppcm-create-one-makefile: make sure flag-make exists before using it.

Before the "(when (and (file-exists-p flag-make)" line the flag-make
file is opened via "(cppcm-query-match-line flag-make ..". Move the
latter *after* the file-exists-p check.

Fixes issue #2
upgraded to v0.1.1

provide some hint when executable is missing
Merge branch 'master' of github.com:redguardtoo/cpputils-cmake
more hint message
v0.1.2