re PR go/78789 (Error: no such instruction: `aesenc %xmm0,%xmm2' when compiling libgo/runtime/aeshash.c)

	PR go/78789
    runtime: don't build aeshash.c if the assembler doesn't support it
    
    This is for CentOS 5, whose assembler does not know the aesinc
    instruction.
    
    Fixes GCC PR 78789.
    
    Patch by Uros Bizjak.
    
    Reviewed-on: https://go-review.googlesource.com/34796

From-SVN: r244031