gtk+: Only disable configure cache if needed
gtk+: Only disable configure cache if needed

We only need to disable configure cache if CFLAGS are being set.

freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,nzjrs/cerbero,fluendo/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,AlertMe/cerbero,justinjoy/cerbero,multipath-rtp/cerbero,cee1/cerbero-mac,jackjansen/cerbero,OptoFidelity/cerbero,ramaxlo/cerbero,EricssonResearch/cerbero,OptoFidelity/cerbero,GStreamer/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,atsushieno/cerbero,jackjansen/cerbero-2013,ikonst/cerbero,ramaxlo/cerbero,brion/cerbero,justinjoy/cerbero,flexVDI/cerbero,atsushieno/cerbero,shoreflyer/cerbero,fluendo/cerbero,brion/cerbero,fluendo/cerbero,GStreamer/cerbero,brion/cerbero,superdump/cerbero,lubosz/cerbero,ikonst/cerbero,nirbheek/cerbero-old,lubosz/cerbero,freedesktop-unofficial-mirror/gstreamer-sdk__cerbero,EricssonResearch/cerbero,centricular/cerbero,ramaxlo/cerbero,centricular/cerbero,multipath-rtp/cerbero,jackjansen/cerbero,centricular/cerbero,OptoFidelity/cerbero,ford-prefect/cerbero,freedesktop-unofficial-mirror/gstreamer-sdk__cerbero,cee1/cerbero-mac,lubosz/cerbero,davibe/cerbero,ylatuya/cerbero,superdump/cerbero,ikonst/cerbero,nirbheek/cerbero,shoreflyer/cerbero,AlertMe/cerbero,GStreamer/cerbero,sdroege/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,cee1/cerbero-mac,ford-prefect/cerbero,ramaxlo/cerbero,nzjrs/cerbero,EricssonResearch/cerbero,flexVDI/cerbero,BigBrother-International/gst-cerbero,ramaxlo/cerbero,ford-prefect/cerbero,jackjansen/cerbero-2013,nzjrs/cerbero,EricssonResearch/cerbero,AlertMe/cerbero,cee1/cerbero-mac,ylatuya/cerbero,nzjrs/cerbero,AlertMe/cerbero,nicolewu/cerbero,nirbheek/cerbero,centricular/cerbero,BigBrother-International/gst-cerbero,ylatuya/cerbero,sdroege/cerbero,justinjoy/cerbero,freedesktop-unofficial-mirror/gstreamer-sdk__cerbero,davibe/cerbero,freedesktop-unofficial-mirror/gstreamer-sdk__cerbero,fluendo/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,superdump/cerbero,nirbheek/cerbero-old,OptoFidelity/cerbero,davibe/cerbero,justinjoy/cerbero,BigBrother-International/gst-cerbero,ford-prefect/cerbero,BigBrother-International/gst-cerbero,ikonst/cerbero,superdump/cerbero,nirbheek/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,nirbheek/cerbero,jackjansen/cerbero-2013,AlertMe/cerbero,atsushieno/cerbero,centricular/cerbero,GStreamer/cerbero,sdroege/cerbero,flexVDI/cerbero,jackjansen/cerbero-2013,ikonst/cerbero,jackjansen/cerbero,shoreflyer/cerbero,brion/cerbero,sdroege/cerbero,flexVDI/cerbero,jackjansen/cerbero-2013,fluendo/cerbero,nicolewu/cerbero,GStreamer/cerbero,jackjansen/cerbero,shoreflyer/cerbero,freedesktop-unofficial-mirror/gstreamer-sdk__cerbero,shoreflyer/cerbero,davibe/cerbero,sdroege/cerbero,brion/cerbero,lubosz/cerbero,atsushieno/cerbero,flexVDI/cerbero,nicolewu/cerbero,nirbheek/cerbero-old,nzjrs/cerbero,BigBrother-International/gst-cerbero,atsushieno/cerbero,multipath-rtp/cerbero,nirbheek/cerbero-old,ylatuya/cerbero,EricssonResearch/cerbero,multipath-rtp/cerbero,multipath-rtp/cerbero