gcc: create symbolic link to ld-linux in EABIhf/gcc 4.7/eglibc

When using eglibc, the ld-linux loader is installed as
ld-linux-armhf.so.3, but gcc 4.7.x was not yet updated, and generates
binaries that reference ld-linux.so.3. This was fixed starting with
gcc 4.8.x. In order to be able to use gcc 4.7, we create the
appropriate symbolic link.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>