debug/gdb: fix runtime sysroot

This patch sets the runtime sysroot to fix the following GDB warning:
"Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code."

The sysroot can later be changed within gdb with the `set sysroot`
command if necessary.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>
(transplanted from 7690196856ce4a4700d1887cc3adf80acc627c52)

configure: add yet a bit more of autostuff compatibility

Well, at least it helps buildroot! :-)

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts, cc/gcc: do not fail on existing symlinks or build.log

If the user builds a toolchain over an existing one, so, without removing
CT_PREFIX_DIR, the build fails as the symlinks already exist, as does the
build.log.

This can also happen (for build.log) if the user first ran in download-
or extract-only.

Patch (with no SoB) originally from:
Phil Wilshire <phil.wilshire@overturenetworks.com>

Modified by me as it did not apply cleanly.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/xldd: fix missing arg to one printf

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/xldd: don't pass random format to printf

Although proabaly inoffensive in our case, do not pass un-checked
formats to printf.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/xldd: print end of current action

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/xldd: fix typo

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

cc/gcc: do not build libgomp or libmudflap in the core steps

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/internals: do not remove lib{32,64}/ symlinks after build

During the build, we create lib{32,64}/ symlinks out of the sysroot.
In some cases (eg. mingw32 target), these symlinks are still required
when running the toolchain. For other combinations, the symlinks are
without incidence, so they can be safely kept after the build.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts: on startup, also remove the buildtools dir

In case there's one lingering around (whether the previous build was
successful, or failed), we have to remove the buildtools directory
as well as the toochain build dir.

This should also fix the case where out makeinfo wrapper calls
itself recursively.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>