arch: add softfp support

Some architectures support a mixed hard/soft floating point, where
the compiler emits hardware floating point instructions, but passes
the operands in core (aka integer) registers.

For example, ARM supports this mode (to come in the next changeset).

Add support for softfp cross compilers to the GCC and GLIBC
configuration. Needed for Ubuntu and other distros that are softfp.

Signed-off-by: Michael Hope <michael.hope@linaro.org>
[yann.morin.1998@anciens.enib.fr: split the original patch]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Menu for the native GDB

config GDB_NATIVE

    bool

    prompt "Native gdb"

    depends on ! BARE_METAL

    depends on ! BACKEND

    help

      Build and install a native gdb for the target, to run on the target.

if GDB_NATIVE

config GDB_NATIVE_STATIC

    bool

    prompt "Build a static native gdb"

    help

      In case you have trouble with dynamic loading of shared libraries,

      you will find that a static gdb comes in handy.

endif # GDB_NATIVE