qmake: resolve relative paths in .pri files relative to the file being included, not the file that does the including

qmake resolves relative path names in included .pri files relative to the file including the .pri file and not relative to the .pri file being included.

Example:

/foo/foo.pri contains:

HEADERS += foo.h
SOURCER += foo.cpp

foo/bar/bar.pro contains:

include(../foo.pri)

Running qmake in /foo/bar/bar.pro results in warning messages about failures to find foo.h and foo.cpp.

This can be worked around by prepending all file paths in the included files with $$PWD, or adding DEPENDPATH += $$PWD to the .pri file.

However, it would be nice if qmake would resolve the included file paths relative to the included file.

Note that if the pro reader behavior for qmake is changed, it should also be changed for the pro reader for other tools like lupdate.