uclibc: uclibc-menuconfig: don't depend on gcc/binutils

uclibc: uclibc-menuconfig: don't depend on gcc/binutils

With the move of uclibc to package/uclibc, the uclibc-menuconfig target now
depends on uclibc-configure, which brings in the build of
binutils/gcc-initial/mpfr/gmp, causing it to take ages with a clean tree.

Fix it by moving the basic .config mangling to the patch step, and depend
on that for menuconfig instead.

Notice that this is broken for _OVERRIDE_SRCDIR users, just like for
busybox, but as that is presumably a small subset of the buildroot
user base (and these advanced users can just run menuconfig in their
local uClibc tree), so this is considered the lesser evil of the two.

The proposed out-of-tree build series will also cause problems with
this.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>