package/makedumpfile: set CROSS

Set CROSS variable otherwise makedumpfile will use it to undefine the
host architecture through -U__$(HOST_ARCH)__ if $(TARGET) is not equal
to $(HOST_ARCH). This will result in the following build failure since
the addition of the package in commit
adb64a97e79bcb4e28450dd858654003ec8706c3 if aarch64_be is cross-compiled
on a aarch64 host for example:

/home/autobuild/autobuild/instance-5/output-1/host/bin/aarch64_be-buildroot-linux-uclibc-gcc -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -O3 -g0  -g -O2 -Wall -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DVERSION='"1.7.0"' -DRELEASE_DATE='"8 Nov 2021"' -D__aarch64_be__ -U__aarch64__ -DUSELZO -c -o ./print_info.o print_info.c

[...]

makedumpfile.c: In function 'is_kvaddr':
makedumpfile.c:1547:46: error: 'KVBASE' undeclared (first use in this function)
 1547 |         return (addr >= (unsigned long long)(KVBASE));
      |                                              ^~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/e4e10364e1a24099ce31bf20eacf5adedf93e5a7

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit b8665e39f1fa3f77fc390cb2a14884f2cb7c76f4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/makedumpfile/makedumpfile.mk

@@ -17,6 +17,7 @@ MAKEDUMPFILE_TARGET = $(BR2_ARCH)
 endif
 
 MAKEDUMPFILE_MAKE_OPTS = \
+	CROSS= \
 	TARGET=$(MAKEDUMPFILE_TARGET) \
 	LINKTYPE=dynamic