The asm file fails to build if we use a modern assembler
which checks that the machine is consistent with the 
filetype.  Fixed by adjusting in a similar manner to 
other assembler.

libgcc/

2019-05-12  Iain Sandoe  <iain@sandoe.co.uk>

	* config/rs6000/darwin-vecsave.S: Set .machine appropriately.

From-SVN: r271111