Ninja builds fail

[Gabor Buella]

The way gtest is added in tests/posix/CMakeLists.txt works well with makefiles, but apparently something is missing for ninja to understand the dependencies.

~/code/pmemfile$ mkdir nbuild && cd nbuild
~/code/pmemfile/nbuild$ cmake -G Ninja .. > /dev/null
~/code/pmemfile/nbuild$ ninja
ninja: error: 'tests/posix/gtest/src/gtest-build/googlemock/gtest/libgtest.a', needed by 'tests/posix/file_crash', missing and no known rule to make it

[Marcin Ślusarz]

Already fixed.

[Gabor Buella]

Oh, I'm also planning to add a travis configuration that builds using ninja.