rt: regression patch for ARM assembly code

Regression Path for ARM build failure on #5647

no need to add extra header for ARM assmebly code. already "RW" not "RWX"

readelf -lW arm-linux-androideabi/lib/libcore-c3ca5d77d81b46c1-0.6.so arm-linux-androideabi/lib/librustrt.so arm-linux-androideabi/lib/libstd-4782a756585a81-0.6.so  | grep GNU_STACK

  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0
  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0
  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0