qt4: Fix kmap2qmap build with clang

qt4: Fix kmap2qmap build with clang

Adapted and backported https://codereview.qt-project.org/#/c/107464/

Fixes errors like
../../include/QtCore/../../src/corelib/tools/qalgorithms.h:161:20:
error: call to function 'operator<' that is neither visible in the
template definition nor found by argument-dependent lookup
        return (t1 < t2);

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>