Fix target detection on mingw32
Fix target detection on mingw32

gcc -dumpmachine returns only 'mingw32'

Change-Id: I774d05a97c5131fc12009e436712c319e54490a5

thdav/aom,jdm/libvpx,stewnorriss/libvpx,abwiz0086/webm.libvpx,lyx2014/libvpx_c,charup/https---github.com-webmproject-libvpx-,Maria1099/webm.libvpx,altogother/webm.libvpx,zofuthan/libvpx,smarter/aom,shyamalschandra/libvpx,kleopatra999/webm.libvpx,iniwf/webm.libvpx,Suvarna1488/webm.libvpx,turbulenz/libvpx,iniwf/webm.libvpx,kleopatra999/webm.libvpx,shacklettbp/aom,running770/libvpx,zofuthan/libvpx,jmvalin/aom,cinema6/libvpx,mwgoldsmith/libvpx,luctrudeau/aom,matanbs/vp982,reimaginemedia/webm.libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,charup/https---github.com-webmproject-libvpx-,mwgoldsmith/libvpx,ittiamvpx/libvpx,vasilvv/esvp8,turbulenz/libvpx,Suvarna1488/webm.libvpx,pcwalton/libvpx,shareefalis/libvpx,goodleixiao/vpx,jacklicn/webm.libvpx,altogother/webm.libvpx,mbebenita/aom,gshORTON/webm.libvpx,mwgoldsmith/vpx,hsueceumd/test_hui,jdm/libvpx,jdm/libvpx,matanbs/vp982,stewnorriss/libvpx,liqianggao/libvpx,turbulenz/libvpx,felipebetancur/libvpx,zofuthan/libvpx,mwgoldsmith/libvpx,running770/libvpx,matanbs/vp982,openpeer/libvpx_new,altogother/webm.libvpx,abwiz0086/webm.libvpx,kalli123/webm.libvpx,reimaginemedia/webm.libvpx,mbebenita/aom,openpeer/libvpx_new,ittiamvpx/libvpx-1,ittiamvpx/libvpx-1,shareefalis/libvpx,Maria1099/webm.libvpx,reimaginemedia/webm.libvpx,vasilvv/esvp8,Distrotech/libvpx,pcwalton/libvpx,GrokImageCompression/aom,Maria1099/webm.libvpx,Topopiccione/libvpx,matanbs/webm.libvpx,shacklettbp/aom,webmproject/libvpx,running770/libvpx,GrokImageCompression/aom,ShiftMediaProject/libvpx,enmasse-entertainment/libvpx,pcwalton/libvpx,sanyaade-teachings/libvpx,WebRTC-Labs/libvpx,felipebetancur/libvpx,felipebetancur/libvpx,jmvalin/aom,vasilvv/esvp8,thdav/aom,liqianggao/libvpx,abwiz0086/webm.libvpx,Topopiccione/libvpx,vasilvv/esvp8,Acidburn0zzz/webm.libvpx,gshORTON/webm.libvpx,enmasse-entertainment/libvpx,turbulenz/libvpx,reimaginemedia/webm.libvpx,smarter/aom,running770/libvpx,genesi/libvpx0,cinema6/libvpx,altogother/webm.libvpx,n4t/libvpx,kim42083/webm.libvpx,sanyaade-teachings/libvpx,felipebetancur/libvpx,jacklicn/webm.libvpx,hsueceumd/test_hui,shacklettbp/aom,charup/https---github.com-webmproject-libvpx-,matanbs/webm.libvpx,Laknot/libvpx,shyamalschandra/libvpx,ittiamvpx/libvpx-1,ittiamvpx/libvpx,cinema6/libvpx,VTCSecureLLC/libvpx,Laknot/libvpx,rikaunite/gst-opera_libvpx,ShiftMediaProject/libvpx,kim42083/webm.libvpx,mwgoldsmith/libvpx,Distrotech/libvpx,thdav/aom,openpeer/libvpx_new,Laknot/libvpx,abwiz0086/webm.libvpx,enmasse-entertainment/libvpx,VTCSecureLLC/libvpx,WebRTC-Labs/libvpx,kleopatra999/webm.libvpx,lyx2014/libvpx_c,shacklettbp/aom,ittiamvpx/libvpx,Suvarna1488/webm.libvpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,mwgoldsmith/vpx,matanbs/vp982,jmvalin/aom,WebRTC-Labs/libvpx,turbulenz/libvpx,rikaunite/gst-opera_libvpx,thdav/aom,genesi/libvpx0,zofuthan/libvpx,ittiamvpx/libvpx,stewnorriss/libvpx,mbebenita/aom,jacklicn/webm.libvpx,hsueceumd/test_hui,cinema6/libvpx,charup/https---github.com-webmproject-libvpx-,turbulenz/libvpx,shyamalschandra/libvpx,VTCSecureLLC/libvpx,Distrotech/libvpx,Topopiccione/libvpx,turbulenz/libvpx,smarter/aom,altogother/webm.libvpx,vasilvv/esvp8,jacklicn/webm.libvpx,cinema6/libvpx,Acidburn0zzz/webm.libvpx,openpeer/libvpx_new,reimaginemedia/webm.libvpx,ittiamvpx/libvpx-1,kleopatra999/webm.libvpx,kim42083/webm.libvpx,matanbs/webm.libvpx,genesi/libvpx0,iniwf/webm.libvpx,VTCSecureLLC/libvpx,enmasse-entertainment/libvpx,running770/libvpx,cinema6/libvpx,jacklicn/webm.libvpx,goodleixiao/vpx,goodleixiao/vpx,zofuthan/libvpx,shyamalschandra/libvpx,cinema6/libvpx,pcwalton/libvpx,hsueceumd/test_hui,kalli123/webm.libvpx,zofuthan/libvpx,kim42083/webm.libvpx,mwgoldsmith/vpx,thdav/aom,altogother/webm.libvpx,mwgoldsmith/libvpx,Laknot/libvpx,kalli123/webm.libvpx,awatry/libvpx.opencl,shyamalschandra/libvpx,Laknot/libvpx,lyx2014/libvpx_c,sanyaade-teachings/libvpx,n4t/libvpx,pcwalton/libvpx,vasilvv/esvp8,goodleixiao/vpx,kim42083/webm.libvpx,matanbs/vp982,GrokImageCompression/aom,genesi/libvpx0,Maria1099/webm.libvpx,Suvarna1488/webm.libvpx,turbulenz/libvpx,smarter/aom,jdm/libvpx,genesi/libvpx0,matanbs/webm.libvpx,n4t/libvpx,lyx2014/libvpx_c,jacklicn/webm.libvpx,GrokImageCompression/aom,abwiz0086/webm.libvpx,kalli123/webm.libvpx,rikaunite/gst-opera_libvpx,Suvarna1488/webm.libvpx,iniwf/webm.libvpx,jmvalin/aom,Maria1099/webm.libvpx,luctrudeau/aom,Topopiccione/libvpx,Laknot/libvpx,mwgoldsmith/vpx,Acidburn0zzz/webm.libvpx,shareefalis/libvpx,shareefalis/libvpx,Distrotech/libvpx,Acidburn0zzz/webm.libvpx,stewnorriss/libvpx,webmproject/libvpx,sanyaade-teachings/libvpx,GrokImageCompression/aom,mbebenita/aom,openpeer/libvpx_new,Topopiccione/libvpx,webmproject/libvpx,luctrudeau/aom,luctrudeau/aom,WebRTC-Labs/libvpx,VTCSecureLLC/libvpx,felipebetancur/libvpx,shacklettbp/aom,rikaunite/gst-opera_libvpx,jdm/libvpx,n4t/libvpx,webmproject/libvpx,webmproject/libvpx,lyx2014/libvpx_c,stewnorriss/libvpx,ShiftMediaProject/libvpx,mbebenita/aom,charup/https---github.com-webmproject-libvpx-,sanyaade-teachings/libvpx,iniwf/webm.libvpx,genesi/libvpx0,turbulenz/libvpx,charup/https---github.com-webmproject-libvpx-,matanbs/webm.libvpx,matanbs/vp982,mwgoldsmith/vpx,ittiamvpx/libvpx-1,gshORTON/webm.libvpx,abwiz0086/webm.libvpx,mbebenita/aom,matanbs/webm.libvpx,Acidburn0zzz/webm.libvpx,mbebenita/aom,openpeer/libvpx_new,goodleixiao/vpx,kim42083/webm.libvpx,rikaunite/gst-opera_libvpx,smarter/aom,liqianggao/libvpx,iniwf/webm.libvpx,GrokImageCompression/aom,reimaginemedia/webm.libvpx,shacklettbp/aom,shareefalis/libvpx,Distrotech/libvpx,mbebenita/aom,Distrotech/libvpx,gshORTON/webm.libvpx,smarter/aom,n4t/libvpx,kleopatra999/webm.libvpx,liqianggao/libvpx,awatry/libvpx.opencl,kalli123/webm.libvpx,jmvalin/aom,liqianggao/libvpx,liqianggao/libvpx,enmasse-entertainment/libvpx,luctrudeau/aom,Acidburn0zzz/webm.libvpx,kalli123/webm.libvpx,shareefalis/libvpx,gshORTON/webm.libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,luctrudeau/aom,jdm/libvpx,stewnorriss/libvpx,running770/libvpx,hsueceumd/test_hui,thdav/aom,gshORTON/webm.libvpx,kleopatra999/webm.libvpx,Suvarna1488/webm.libvpx,shyamalschandra/libvpx,Maria1099/webm.libvpx,awatry/libvpx.opencl,Topopiccione/libvpx,vasilvv/esvp8,ittiamvpx/libvpx,hsueceumd/test_hui,jmvalin/aom,matanbs/vp982,goodleixiao/vpx,WebRTC-Labs/libvpx,ShiftMediaProject/libvpx,awatry/libvpx.opencl,ittiamvpx/libvpx,mbebenita/aom,lyx2014/libvpx_c,pcwalton/libvpx,ittiamvpx/libvpx-1