Specify the QtSvg requirement in the 'find_package(Qt4...)' line.
Also, change the linking order in the MinGW-w64 case, apparently the
build now fails without this.
[...]/qt/plugins/imageformats/libqsvg.a(qsvgiohandler.o):\
qsvgiohandler.cpp:(.text+0x571):
undefined reference to `QSvgRenderer::load(QByteArray const&)'
[...]