This way it always shows up in ccmake, even if not defined.
A string is used instead of path because I personally think it makes more
sense in the following use-cases:
STRING:
-DCMAKE_INSTALL_PREFIX=/home/user -DCMAKE_INSTALL_BINDIR=bins
installs everything to /home/user/{lib,etc,share,(...)} and executables to
${CMAKE_INSTALL_PREFIX}/bins
-DCMAKE_INSTALL_PREFIX=/home/user -DCMAKE_INSTALL_BINDIR=/opt/bin
everything to /home/user/{lib,etc,share,(...)} and executables to
/opt/bin
PATH:
-DCMAKE_INSTALL_PREFIX=/home/user -DCMAKE_INSTALL_BINDIR=bins
everything to /home/user/{lib,etc,share,(...)} and executables to
$(pwd)/bins (!)
-DCMAKE_INSTALL_PREFIX=/home/user -DCMAKE_INSTALL_BINDIR=/opt/bin
same as STRING
The lib used to return "" for both properly detected ASCII and
detection failure. And the tool would return "ascii/unknown".
Make a proper distinction between the 2 cases.
