[driver] Remove obsolete support for -A link option. The standard -A option is

used by the preprocessor.  Apple's GCC also supported a -A option for linking.

The ld man page has the following:
 -A basefile - Obsolete incremental load format.  This option is obsolete.

Nick Kledzik confirms this option is no longer needed/supported.
rdar://11455614

llvm-svn: 156965