gcc: immediate changes to arc-2015.12-rc1

These patches solve several problems that were discovered
after bumping tools to arc-2015.12-rc1.

The fixes were done in development tree arc-4.8-dev and will be
a part of the next release of ARC GNU tools.
Once that new release happens these patches must be removed.

Signed-off-by: Lada Trimasova <ltrimas@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>