Partially revert 7a368ab06b4926236ec93207e66ff7b14c234fe1

If we #include "qt-ui/ui_anything" from anywhere, the Makefile rules
will blow up.

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Ensure that uic is always run before any C++ source is compiled

It's very, very hard to scan for dependencies with a plain make. So
let's give up and simply enforce that all *.ui files need to be
processed before a *.cpp gets compiled.

This introduces the make target "uicables" (similar to the "mocables"
target that qmake produces) that will compile all .ui files. This
target is now a dependency of all .cpp builds.

In addition, tell make where to find .ui files and their corresponding
ui_*.h files.

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Create the .uic/qt-ui directory

This appears to be missing from commit 565ae2fe89dc ("Ensure that uic is
always run before any C++ source is compiled").

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>