libgcc: Ensure that gcc configure options are passed to libgcc too

libgcc: Ensure that gcc configure options are passed to libgcc too

libgcc uses certain options from EXTRA_OECONF as well, curently we are
ignoring them, as a result we do not configure libgcc to match cross gcc
in some cases e.g. ppc/musl should have used 64bit long doubles but
it went for 128-ldbls which is default, works on glibc but not on musl

(From OE-Core rev: d774bb2d10f2c05900f87dcc53f073433ca02121)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>