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>
(transplanted from 1ebc2248cc60230cd53ff94ae8f8f1e3261461a3)

2008-04-28  Hiroki Kaminaga  <kaminaga@sm.sony.co.jp>

	[BZ 6740]

	nptl/sysdeps/powerpc/tcb-offsets.sym (PRIVATE_FUTEX_OFFSET):

	Guard sym definition with #ifndef __ASSUME_PRIVATE_FUTEX.

--- a/nptl/sysdeps/powerpc/tcb-offsets.sym

+++ b/nptl/sysdeps/powerpc/tcb-offsets.sym

@@ -15,4 +15,6 @@

 PID				thread_offsetof (pid)

 TID				thread_offsetof (tid)

 POINTER_GUARD			(offsetof (tcbhead_t, pointer_guard) - TLS_TCB_OFFSET - sizeof (tcbhead_t))

+#ifndef __ASSUME_PRIVATE_FUTEX

 PRIVATE_FUTEX_OFFSET		thread_offsetof (header.private_futex)

+#endif