Don't use STREQUAL to test the BUILD_TESTS option

True is 1, ON, YES, TRUE, Y, or a non-zero number.
For example: Using -DBUILD_TESTS=YES would evaluate to FALSE, which is an
unexpected behavior.

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
test: Removes meaningless add_dependencies(..... razorqt)

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Adds Qt5Widgets to the required pkg-config required packages

Thanks-to: Pier Luigi Fiorini <pierluigi.fiorini@gmail.com>
Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Updates CMake's minimum required version

GNUInstallDirs debuted with the v2.8.5
It's not clear to me if this requirement is OK for everybody!

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Merge pull request #8 from luis-pereira/maint-build-system

Build system maintenance