Update driver and libgcc configuration for dynamic linking

This makes the GCC driver pass the right options to the linker
for dynamic linking with glibc.  It also updates the libgcc
configuration for NaCl as appropriate for the glibc build.  The
libgcc build is still affected by the --with-newlib configure
switch, because we need that configuration to build the bootstrap
libgcc used when building glibc.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3068
TEST= hand-tested toolchain update

Change-Id: I90f529677e709dd43a0ca4f5f39cc8a018c17241
3 files changed