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)

diff -urN uClibc-dist/libc/sysdeps/linux/common/bits/uClibc_touplow.h uClibc/libc/sysdeps/linux/common/bits/uClibc_touplow.h

--- uClibc-dist/libc/sysdeps/linux/common/bits/uClibc_touplow.h   Fri Jun  3 13:30:25 2005

+++ uClibc/libc/sysdeps/linux/common/bits/uClibc_touplow.h   Fri Jun  3 13:30:39 2005

@@ -34,11 +34,11 @@

 /* glibc uses the equivalent of - typedef __int32_t __ctype_touplow_t; */

-typedef __uint16_t __ctype_mask_t;

+typedef __uint32_t __ctype_mask_t;

 #ifdef __UCLIBC_HAS_CTYPE_SIGNED__

-typedef __int16_t __ctype_touplow_t;

+typedef __int32_t __ctype_touplow_t;

 #define __UCLIBC_CTYPE_B_TBL_OFFSET       128

 #define __UCLIBC_CTYPE_TO_TBL_OFFSET      128