There are many 3rd-party libraries with a quite complex build process, which is already implemented in .pro, Makefile, Makefile.am, CMakeFiles.txt or .xcodeproj.

In qmake there are no integration for such subprojects. User can add new build step in QtCreator project settings, or play with QMAKE_EXTRA_TARGETS and QMAKE_EXTRA_COMPILERS to achieve correct build. In such case clean action does not automatically call "make clean" for implicitly referenced makefile, and QtCreator integration not exist at all.

Expected behavior:

• qbs keeps in project file and exposes via API information about subproject: working directory, target file, maybe type of alien build system, clean/tests/install step status (i.e is it allowed or prohibited)
• QtCreator allows to add subproject of any supported type with wizard, and writes it to qbs file (using qbs API?).
• QtCreator opens alien subprojects as usual: shows in project tree, reads compiler options, adds files to index.