Need --divide flag for assembly of startup.S on some platforms

[Seth Goldberg]

Hi,

  When assembling grub-core/kern/i386/pc/startup.S, gas on some platforms 
chokes on this line:

       movl    $((LOCAL(bypass_table_end) - LOCAL(bypass_table)) / 2), %ecx

 Because on non i386-linux targets, '/' is used as a comment delimiter for 
compatibility purposes.  This can be overridden with the --divide switch.

  Since the default for gas on these platforms is to use he division operator 
as a comment delimiter, the "-Wa,--divide" flags need to be passed on the 
gcc command line when assembling such files.

 --S