README.xbuild update

*** 21,31 ****
  pfexec tar xvzf armtc.tar.gz -C /
  find /opt/armtc
  
  Fun way:
  
! Clone this repository again and do a normal i386 on i386 build.
  mkdir -p /opt/armtc/lib/amd64 /opt/armtc/usr/bin/amd64
  cd /opt/armtc/lib/
  ln -s amd64 64
  cd ../usr/bin
  ln -s amd64 64
--- 21,36 ----
  pfexec tar xvzf armtc.tar.gz -C /
  find /opt/armtc
  
  Fun way:
  
! Using a normal i386 on i386 build:
! cd usr/src
! dmake setup
! cd cmd/sgs
! dmake install
! 
  mkdir -p /opt/armtc/lib/amd64 /opt/armtc/usr/bin/amd64
  cd /opt/armtc/lib/
  ln -s amd64 64
  cd ../usr/bin
  ln -s amd64 64