cc/gcc: Add the ability to build gcc from svn

I took some of the svn functionality from eglibc.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
[yann.morin.1998@free.fr: fix the conditional test in build script]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

# Compute M68k-specific values

CT_DoArchTupleValues() {

    :

}