[poppler] cmake issues

[Adrian Johnson]

As the autotools build will be dropped I've been gaining more experience
with the cmake build. I've found a few problems:

1) Is there any way to selectively disable the fontends? If I'm working
on core I like to minimize the rebuild times.

2) I usually install cairo git and poppler git to their own prefix for
testing. I compile popper with PKG_CONFIG_PATH set to this location so
it will link with cairo git. poppler-glib-demo is failing to link with
cairo. pdftocairo links fine. I noticed this because there is some new
API in cairo git and I have a poppler branch with support for this API.

The problem is the poppler-glib-demo link command lists "-lcairo" then
the libcairo.so. Manually running the link command without "-lcairo" (or
even just putting it after the libcairo.so) fixes the linking. The
pdftocairo link command does not have "-lcairo".

I don't know how to fix this in cmake. I assume it is the linking with
gtk3 that is adding the -lcairo. I tried adding ${CAIRO_LIBRARIES}
before ${GTK3_LIBRARIES} in glib/demo/CMakeLists.txt but it still fails
to link.

3) What is the preferred way to run cmake. In the top level dir? Or
create a build dir and run it in that? If I build in the top level dir,
git status shows a lot of build noise that has not been added to
.gitignore. I have to run git clean to clean it up. Whichever way is
best we should add the build output to .gitignore to hide it from git
status.