This commit adds a "CMake Install" deployment step, which is using
"cmake --install" command.
"cmake --install" command has been added in CMake 3.15, this is why the
minimum CMake version has been updated to 3.15.
Note that CMakeBuildSystem::makeInstallCommand is still using cmake --
build --target install due to a CMake bug regarding "Ninja Multi-Config"
generator, which doesn't intall all binaries via "cmake --install".
Fixes: QTCREATORBUG-25880
Change-Id: I504674c380055d8ef136d344a78b80c17ecf9765
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>