kbuild: Use $(obj)/%.cc to fix host C++ module builds

JIRA: https://issues.redhat.com/browse/RHEL-107194

commit 7ed9d13
Author: Nicolas Schier <n.schier@avm.de>
Date:   Mon Jun 24 13:12:14 2024 +0200

    kbuild: Use $(obj)/%.cc to fix host C++ module builds

    Use $(obj)/ instead of $(src)/ prefix when building C++ modules for
    host, as explained in commit b1992c3 ("kbuild: use $(src) instead
    of $(srctree)/$(src) for source directory").  This fixes build failures
    of 'xconfig':

        $ make O=build/ xconfig
        make[1]: Entering directory '/data/linux/kbuild-review/build'
          GEN     Makefile
        make[3]: *** No rule to make target '../scripts/kconfig/qconf-moc.cc', needed by 'scripts/kconfig/qconf-moc.o'.  Stop.

    Fixes: b1992c3 ("kbuild: use $(src) instead of $(srctree)/$(src) for source directory")
    Reported-by: Rolf Eike Beer <eb@emlix.com>
    Signed-off-by: Nicolas Schier <n.schier@avm.de>
    Tested-by: Rolf Eike Beer <eb@emlix.com>
    Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Signed-off-by: Herton R. Krzesinski <herton@redhat.com>

Author: Herton R. Krzesinski

scripts/Makefile.host

@@ -125,7 +125,7 @@ $(call multi_depend, $(host-cxxmulti), , -objs -cxxobjs)
 # Create .o file from a single .cc (C++) file
 quiet_cmd_host-cxxobjs	= HOSTCXX $@
       cmd_host-cxxobjs	= $(HOSTCXX) $(hostcxx_flags) -c -o $@ $<
-$(host-cxxobjs): $(obj)/%.o: $(src)/%.cc FORCE
+$(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
 	$(call if_changed_dep,host-cxxobjs)
 
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \