syslinux: Set LD to avoid using build host ld

syslinux: Set LD to avoid using build host ld

base ld is used during link phase and since its x86 so it
works mostly, however it can cause problems depending upon
build host. During cross build we should use cross linker
Fixes errors e.g.

ld -shared -m elf_i386 --hash-style=gnu -T
/home/ubuntu/work/oe/openembedded-core/build/tmp-glibc/work/i586-oe-linux/syslinux/6.03-r0/syslinux-6.03/com32/lib/i386/elf.ld
-soname libcom32.c32 -o libcom32.elf zlib/adler32.o zlib/compress.
o zlib/crc32.o zlib/uncompr.o zlib/deflate.o zlib/trees.o zlib/zutil.o
zlib/inflate.o zlib/infback.o zlib/inftrees.o zlib/inffast.o sys/zfile.o
sys/zfopen.o libpng/png.o libpng/pngset.o libpng/pngget.o
libpng/pngrutil.o libpng/pngtrans.o
libpng/pngwutil.o libpng/pngread.o libpng/pngrio.o libpng/pngwio.o
libpng/pngwrite.o libpng/pngrtran.o libpng/pngwtran.o libpng/pngmem.o
libpng/pngerror.o libpng/pngpread.o jpeg/tinyjpeg.o jpeg/jidctflt.o
jpeg/decode1.o jpeg/decode3.o jpe
g/rgb24.o jpeg/bgr24.o jpeg/yuv420p.o jpeg/grey.o jpeg/rgba32.o
jpeg/bgra32.o pci/cfgtype.o pci/scan.o pci/bios.o pci/readb.o
pci/readw.o pci/readl.o pci/writeb.o pci/writew.o pci/writel.o
sys/vesacon_write.o sys/vesaserial_write.o sys/ve
sa/initvesa.o sys/vesa/drawtxt.o sys/vesa/background.o
sys/vesa/alphatbl.o sys/vesa/screencpy.o sys/vesa/fmtpixel.o
sys/vesa/i915resolution.o syslinux/reboot.o syslinux/keyboard.o
syslinux/version.o syslinux/pxe_get_cached.o syslinux/pxe_get_nic.o
syslinux/pxe_dns.o syslinux/video/fontquery.o
syslinux/video/reportmode.o syslinux/addlist.o syslinux/freelist.o
syslinux/memmap.o syslinux/movebits.o syslinux/shuffle.o
syslinux/shuffle_pm.o syslinux/shuffle_rm.o syslinux/bios$oot.o
syslinux/zonelist.o syslinux/dump_mmap.o syslinux/dump_movelist.o
syslinux/run_default.o syslinux/run_command.o syslinux/cleanup.o
syslinux/localboot.o syslinux/runimage.o syslinux/loadfile.o
syslinux/floadfile.o syslinux/zloadfile$o syslinux/load_linux.o
syslinux/initramfs.o syslinux/initramfs_file.o
syslinux/initramfs_loadfile.o syslinux/initramfs_archive.o sys/libansi.o
sys/gpxe.o atexit.o onexit.o abort.o
| ld: zlib/deflate.o: unrecognized relocation (0x2b) in section `.text'
| ld: final link failed: Bad value
| make[4]: *** [libcom32.elf] Error 1

Signed-off-by: Khem Raj <raj.khem@gmail.com>