scripts: remove . from $PATH

Add CT_SanitizePath function which removes entries referring to ., /tmp
and non-existing directories from $PATH, and call it early in the
build script.

If . is in PATH, gcc-4.4.4 build breaks:

[ALL ] checking what assembler to use...
/tmp/build/targets/arm-unknown-linux-uclibcgnueabi/build/gcc-core-static/arm-unknown-linux-uclibcgnueabi/bin/as
...
[ALL ] config.status: creating as

i.e. "as" is supposed to be the arm-unknown-linux-uclibcgnueabi cross assembler,
but config.status creates a local "as" script which is calling the
host assembler.

Signed-off-by: Johannes Stezenbach <js@sig21.net>
[Yann E. MORIN: style fixes + explanations]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from 20dd8cef1c8adff0aa3e78ae6d7acfbc45ed5a83)

Original patch from: ../crosstool-NG/ct-ng.trunk/patches/binutils/2.19/180-libiberty-pic.patch

-= BEGIN original header =-

Original patch from Gentoo:

gentoo/src/patchsets/binutils/2.19/91_all_libiberty-pic.patch

-= END original header =-

diff -durN binutils-2.19.1.orig/libiberty/Makefile.in binutils-2.19.1/libiberty/Makefile.in

--- binutils-2.19.1.orig/libiberty/Makefile.in	2008-07-24 15:51:49.000000000 +0200

+++ binutils-2.19.1/libiberty/Makefile.in	2009-03-08 11:57:03.000000000 +0100

@@ -227,6 +227,7 @@

 	  $(AR) $(AR_FLAGS) $(TARGETLIB) \

 	    $(REQUIRED_OFILES) $(EXTRA_OFILES) $(LIBOBJS); \

 	  $(RANLIB) $(TARGETLIB); \

+	  cp $(TARGETLIB) ../ ; \

 	  cd ..; \

 	else true; fi