qmake with MinGW does not call mkdir -p

When the INSTALLS feature of qmake shall create some directory, it calls mkdir. On a standard Windows installation this calls the mkdir version of windows which creates all non-existent directories in the path (e.g. mkdir a\b\c will create a and b and c also if b and c do not exist) If a Linux shell is available (!isEmpty(QMAKE_SH) in the <QTDIR>\mkspecs\win32-g++) this calls mkdir from Mingw/MSys which does NOT create intermediate directories. So sometimes the make process crashes when creating the directory.

This may be resolved by changing the line:
QMAKE_MKDIR = mkdir
to
QMAKE_MKDIR = mkdir -p
in <QTDIR>\mkspecs\win32-g++, within the !isEmpty(QMAKE_SH)

block (see attatched, changed file!).

In the Unix makespecs this is set the right way via in <QTDIR>/mkspecs/common/linux.conf .