Skip directories with LIBPATH_SUFFIX_SKIP suffix

On Linux/x86-64, when binutils is configured with --libdir=/usr/lib64,
genscripts.sh treats /usr/lib64 as the default search directory.  It
puts /usr/lib64 in linker scripts for all emulations, like

---
/* Script for -z combreloc: combine and sort reloc sections */
OUTPUT_FORMAT("elf32-i386", "elf32-i386",
	      "elf32-i386")
OUTPUT_ARCH(i386)
ENTRY(_start)
SEARCH_DIR("/usr/x86_64-redhat-linux/lib32");
SEARCH_DIR("/usr/i386-redhat-linux/lib32"); SEARCH_DIR("/usr/lib6432");
SEARCH_DIR("/usr/local/lib32"); SEARCH_DIR("/lib32");
SEARCH_DIR("/usr/lib32"); SEARCH_DIR("/usr/i386-redhat-linux/lib");
SEARCH_DIR("/usr/lib64"); SEARCH_DIR("/usr/local/lib");
SEARCH_DIR("/lib"); SEARCH_DIR("/usr/lib");
---

/usr/lib6432 is odd and /usr/lib64 is wrong.  This patch changes
genscripts.sh to check LIBPATH_SUFFIX_SKIP if it is defined.  It
skips directories with LIBPATH_SUFFIX_SKIP suffix.

	PR ld/16456
	* genscripts.sh: Don't search directory with LIBPATH_SUFFIX_SKIP
	suffix.
	* emulparams/elf32_x86_64.sh (LIBPATH_SUFFIX_SKIP): Set to 64
	for elf32_x86_64 emulation.
	* emulparams/elf_i386.sh (LIBPATH_SUFFIX_SKIP): Set to 64
	for elf_i386 emulation.