scripts/decode_stacktrace.sh: prefix addr2line with $CROSS_COMPILE

At least for ARM64 kernels compiled with the crosstoolchain from
Debian/stretch or with the toolchain from kernel.org the line number is
not decoded correctly by 'decode_stacktrace.sh':

  $ echo "[  136.513051]  f1+0x0/0xc [kcrash]" | \
    CROSS_COMPILE=/opt/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux- \
   ./scripts/decode_stacktrace.sh /scratch/linux-arm64/vmlinux \
                                  /scratch/linux-arm64 \
                                  /nfs/debian/lib/modules/4.20.0-devel
  [  136.513051] f1 (/linux/drivers/staging/kcrash/kcrash.c:68) kcrash

If addr2line from the toolchain is used the decoded line number is correct:

  [  136.513051] f1 (/linux/drivers/staging/kcrash/kcrash.c:57) kcrash

Link: http://lkml.kernel.org/r/20190527083425.3763-1-manut@linutronix.deSigned-off-by: Manuel Traut <manut@linutronix.de>
Acked-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/decode_stacktrace.sh

@@ -73,7 +73,7 @@ parse_symbol() {
 	if [[ "${cache[$module,$address]+isset}" == "isset" ]]; then
 		local code=${cache[$module,$address]}
 	else
-		local code=$(addr2line -i -e "$objfile" "$address")
+		local code=$(${CROSS_COMPILE}addr2line -i -e "$objfile" "$address")
 		cache[$module,$address]=$code
 	fi