Define READELF_FOR_TARGET in gcc build

Otherwise realelf won't be found in darwin, and cause
some backend to misbehave.

READELF_FOR_TARGET appears in gcc-4.7, but is backported
to gcc-4.6 as well.

Change-Id: Ia45b3ce046cc68a40862be8f5a906606d2fd0665
Merge remote-tracking branch 'aosp/master'
remove arm-eabi-4.9 and use arm-eabi-4.9 script instead.  gcc 4.9 just isn't stable enough yet
Signed-off-by: Paul Beeler <sparksco@gmail.com>

Change-Id: Ie3f40a4133d569b11b23594eb8b4876ed4955595