configure: defer x32 check until post toolchain setup
configure: defer x32 check until post toolchain setup

x32 would never be detected unless an explicit CC= was used
fixes:
...: -E: command not found

Change-Id: I465fd7b0979f782053bdda240ad68edbca5658e5

GrokImageCompression/aom,Laknot/libvpx,kleopatra999/webm.libvpx,liqianggao/libvpx,goodleixiao/vpx,kim42083/webm.libvpx,kleopatra999/webm.libvpx,Distrotech/libvpx,stewnorriss/libvpx,kleopatra999/webm.libvpx,stewnorriss/libvpx,Distrotech/libvpx,pcwalton/libvpx,charup/https---github.com-webmproject-libvpx-,jdm/libvpx,reimaginemedia/webm.libvpx,mbebenita/aom,shacklettbp/aom,n4t/libvpx,reimaginemedia/webm.libvpx,Maria1099/webm.libvpx,reimaginemedia/webm.libvpx,ittiamvpx/libvpx-1,goodleixiao/vpx,Maria1099/webm.libvpx,matanbs/vp982,openpeer/libvpx_new,smarter/aom,ShiftMediaProject/libvpx,zofuthan/libvpx,iniwf/webm.libvpx,VTCSecureLLC/libvpx,shacklettbp/aom,Laknot/libvpx,VTCSecureLLC/libvpx,thdav/aom,jdm/libvpx,abwiz0086/webm.libvpx,running770/libvpx,running770/libvpx,GrokImageCompression/aom,Distrotech/libvpx,kleopatra999/webm.libvpx,thdav/aom,kleopatra999/webm.libvpx,smarter/aom,altogother/webm.libvpx,Acidburn0zzz/webm.libvpx,hsueceumd/test_hui,felipebetancur/libvpx,mwgoldsmith/libvpx,thdav/aom,running770/libvpx,lyx2014/libvpx_c,jacklicn/webm.libvpx,liqianggao/libvpx,smarter/aom,mwgoldsmith/libvpx,matanbs/vp982,Suvarna1488/webm.libvpx,n4t/libvpx,jacklicn/webm.libvpx,iniwf/webm.libvpx,pcwalton/libvpx,Topopiccione/libvpx,shyamalschandra/libvpx,mwgoldsmith/vpx,jdm/libvpx,abwiz0086/webm.libvpx,shacklettbp/aom,felipebetancur/libvpx,stewnorriss/libvpx,Topopiccione/libvpx,lyx2014/libvpx_c,Suvarna1488/webm.libvpx,mbebenita/aom,shyamalschandra/libvpx,shacklettbp/aom,Maria1099/webm.libvpx,jdm/libvpx,liqianggao/libvpx,felipebetancur/libvpx,jacklicn/webm.libvpx,VTCSecureLLC/libvpx,Suvarna1488/webm.libvpx,matanbs/webm.libvpx,smarter/aom,Suvarna1488/webm.libvpx,jmvalin/aom,mwgoldsmith/vpx,shareefalis/libvpx,reimaginemedia/webm.libvpx,charup/https---github.com-webmproject-libvpx-,abwiz0086/webm.libvpx,goodleixiao/vpx,zofuthan/libvpx,n4t/libvpx,Maria1099/webm.libvpx,mwgoldsmith/vpx,kim42083/webm.libvpx,Suvarna1488/webm.libvpx,GrokImageCompression/aom,hsueceumd/test_hui,kim42083/webm.libvpx,openpeer/libvpx_new,openpeer/libvpx_new,jdm/libvpx,ittiamvpx/libvpx,Topopiccione/libvpx,webmproject/libvpx,gshORTON/webm.libvpx,openpeer/libvpx_new,abwiz0086/webm.libvpx,kalli123/webm.libvpx,jmvalin/aom,matanbs/webm.libvpx,reimaginemedia/webm.libvpx,webmproject/libvpx,kim42083/webm.libvpx,Laknot/libvpx,GrokImageCompression/aom,iniwf/webm.libvpx,reimaginemedia/webm.libvpx,liqianggao/libvpx,pcwalton/libvpx,mbebenita/aom,hsueceumd/test_hui,mwgoldsmith/vpx,stewnorriss/libvpx,Acidburn0zzz/webm.libvpx,goodleixiao/vpx,Acidburn0zzz/webm.libvpx,kalli123/webm.libvpx,luctrudeau/aom,felipebetancur/libvpx,webmproject/libvpx,Topopiccione/libvpx,jacklicn/webm.libvpx,webmproject/libvpx,hsueceumd/test_hui,charup/https---github.com-webmproject-libvpx-,mwgoldsmith/libvpx,running770/libvpx,stewnorriss/libvpx,running770/libvpx,ShiftMediaProject/libvpx,jmvalin/aom,gshORTON/webm.libvpx,matanbs/webm.libvpx,goodleixiao/vpx,shyamalschandra/libvpx,Distrotech/libvpx,ittiamvpx/libvpx-1,VTCSecureLLC/libvpx,hsueceumd/test_hui,mwgoldsmith/vpx,iniwf/webm.libvpx,Maria1099/webm.libvpx,VTCSecureLLC/libvpx,iniwf/webm.libvpx,luctrudeau/aom,matanbs/vp982,Acidburn0zzz/webm.libvpx,ittiamvpx/libvpx-1,pcwalton/libvpx,kalli123/webm.libvpx,matanbs/webm.libvpx,abwiz0086/webm.libvpx,ittiamvpx/libvpx-1,VTCSecureLLC/libvpx,smarter/aom,Acidburn0zzz/webm.libvpx,jacklicn/webm.libvpx,gshORTON/webm.libvpx,shareefalis/libvpx,lyx2014/libvpx_c,shareefalis/libvpx,shareefalis/libvpx,Laknot/libvpx,gshORTON/webm.libvpx,webmproject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,matanbs/vp982,charup/https---github.com-webmproject-libvpx-,mbebenita/aom,shyamalschandra/libvpx,n4t/libvpx,ittiamvpx/libvpx,matanbs/vp982,ShiftMediaProject/libvpx,altogother/webm.libvpx,Distrotech/libvpx,jmvalin/aom,zofuthan/libvpx,jmvalin/aom,iniwf/webm.libvpx,lyx2014/libvpx_c,altogother/webm.libvpx,altogother/webm.libvpx,jacklicn/webm.libvpx,Distrotech/libvpx,luctrudeau/aom,ittiamvpx/libvpx,mbebenita/aom,pcwalton/libvpx,matanbs/vp982,kalli123/webm.libvpx,felipebetancur/libvpx,gshORTON/webm.libvpx,shareefalis/libvpx,Laknot/libvpx,n4t/libvpx,jdm/libvpx,zofuthan/libvpx,felipebetancur/libvpx,mwgoldsmith/libvpx,liqianggao/libvpx,hsueceumd/test_hui,thdav/aom,zofuthan/libvpx,pcwalton/libvpx,lyx2014/libvpx_c,luctrudeau/aom,kleopatra999/webm.libvpx,gshORTON/webm.libvpx,ittiamvpx/libvpx,charup/https---github.com-webmproject-libvpx-,Acidburn0zzz/webm.libvpx,altogother/webm.libvpx,matanbs/webm.libvpx,Laknot/libvpx,Maria1099/webm.libvpx,kalli123/webm.libvpx,mwgoldsmith/libvpx,GrokImageCompression/aom,goodleixiao/vpx,ShiftMediaProject/libvpx,kalli123/webm.libvpx,lyx2014/libvpx_c,abwiz0086/webm.libvpx,shareefalis/libvpx,webmproject/libvpx,thdav/aom,charup/https---github.com-webmproject-libvpx-,Suvarna1488/webm.libvpx,altogother/webm.libvpx,kim42083/webm.libvpx,thdav/aom,openpeer/libvpx_new,ittiamvpx/libvpx-1,shacklettbp/aom,mbebenita/aom,zofuthan/libvpx,liqianggao/libvpx,matanbs/webm.libvpx,mbebenita/aom,ittiamvpx/libvpx,shyama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