kernel/kvm: don't hardcode objcopy

testcases/kernel/kvm uses objcopy to contruct a payload binary, but in
cross builds the host objcopy may not know how to handle target
binaries:

 CC testcases/kernel/kvm/lib_host.o
 objcopy: Unable to recognise the format of the input file `kvm_svm03-payload.elf'
 make[3]: *** [ltp/testcases/kernel/kvm/Makefile:67: kvm_svm03-payload.o] Error 1

This is trivially fixed by searching for an objcopy tool (so
host-prefixed in cross builds) and using that instead.

Link: https://lore.kernel.org/ltp/20250227124330.949015-1-ross.burton@arm.com/
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Ross Burton <ross.burton@arm.com>

Author: rossburton

configure.ac

@@ -30,6 +30,7 @@ AC_PROG_RANLIB
 AC_DEFUN([AC_PROG_STRIP], [AC_CHECK_TOOL(STRIP, strip, :)])
 AC_PROG_STRIP
 AC_PROG_YACC
+AC_CHECK_TOOL([OBJCOPY], [objcopy], [:])
 
 m4_ifndef([PKG_CHECK_EXISTS],
 	[m4_fatal([must install pkg-config or pkgconfig and pkg.m4 macro (usual dependency), see INSTALL])])

include/mk/config.mk.in

@@ -11,6 +11,7 @@ AR			:= @AR@
 CC			:= @CC@
 LEX			:= @LEX@
 RANLIB			:= @RANLIB@
+OBJCOPY			:= @OBJCOPY@
 STRIP			:= @STRIP@
 YACC			:= @YACC@
 

testcases/kernel/kvm/Makefile

@@ -60,11 +60,11 @@ include $(top_srcdir)/include/mk/generic_leaf_target.mk
 %-payload.o: %.c lib_guest.o $(ARCH_OBJ)
 ifdef VERBOSE
 	$(CC) $(GUEST_CPPFLAGS) $(GUEST_CFLAGS) $(GUEST_LDFLAGS) -o $*-payload.elf $^ $(GUEST_LDLIBS)
-	objcopy -O binary -j .init.boot -j .text -j .data -j .init -j .preinit_array -j .init_array --gap-fill=0 $*-payload.elf $*-payload.bin
+	$(OBJCOPY) -O binary -j .init.boot -j .text -j .data -j .init -j .preinit_array -j .init_array --gap-fill=0 $*-payload.elf $*-payload.bin
 	$(KVM_LD) -z noexecstack -r -T $(abs_srcdir)/linker/payload.lds --oformat=$(BIN_FORMAT) -o $@ $*-payload.bin
 else
 	@$(CC) $(GUEST_CPPFLAGS) $(GUEST_CFLAGS) $(GUEST_LDFLAGS) -o $*-payload.elf $^ $(GUEST_LDLIBS)
-	@objcopy -O binary -j .init.boot -j .text -j .data -j .init -j .preinit_array -j .init_array --gap-fill=0 $*-payload.elf $*-payload.bin
+	@$(OBJCOPY) -O binary -j .init.boot -j .text -j .data -j .init -j .preinit_array -j .init_array --gap-fill=0 $*-payload.elf $*-payload.bin
 	@$(KVM_LD) -z noexecstack -r -T $(abs_srcdir)/linker/payload.lds --oformat=$(BIN_FORMAT) -o $@ $*-payload.bin
 	@echo KVM_CC $(target_rel_dir)$@
 endif