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)

YEM-20070519:

bits/sysnum.h needs a cross compiler to be built. Fortunately, this

header is not needed to build gcc. Move generation of this header.

Index: uClibc/Makefile.in

===================================================================

--- uClibc/Makefile.in	(revision 18651)

+++ uClibc/Makefile.in	(working copy)

@@ -91,6 +91,11 @@

 			$(LN) -fs $$i .; \

 		done; \

 	fi

+ifeq ($(UCLIBC_HAS_LOCALE),y)

+	$(MAKE) locale_headers

+endif

+

+pregen: headers

 	$(Q)\

 	set -e; \

 	cd $(top_builddir); \

@@ -102,12 +107,7 @@

 	else \

 		mv -f $$tmp include/bits/sysnum.h; \

 	fi

-ifeq ($(UCLIBC_HAS_LOCALE),y)

-	$(MAKE) locale_headers

-endif

-pregen: headers

-

 install: install_runtime install_dev