install: honor DESTDIR on sysconfdir population

When creating and populating $sysconfdir, we should prepend $DESTDIR
as we do with all other paths.
Reported-by: NFrank Arnold <frank.arnold@amd.com>
Signed-off-by: NAndre Przywara <andre.przywara@amd.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

Makefile

@@ -194,8 +194,8 @@ ifdef CONFIG_POSIX
 endif
 
 install-sysconfig:
-	$(INSTALL_DIR) "$(sysconfdir)/qemu"
-	$(INSTALL_DATA) $(SRC_PATH)/sysconfigs/target/target-x86_64.conf "$(sysconfdir)/qemu"
+	$(INSTALL_DIR) "$(DESTDIR)$(sysconfdir)/qemu"
+	$(INSTALL_DATA) $(SRC_PATH)/sysconfigs/target/target-x86_64.conf "$(DESTDIR)$(sysconfdir)/qemu"
 
 install: all $(if $(BUILD_DOCS),install-doc) install-sysconfig
 	$(INSTALL_DIR) "$(DESTDIR)$(bindir)"