[xen staging] fix build with CONFIG_HYPFS_CONFIG enabled

[patchbot@xxxxxxx]

commit 1c5db7cc7a7080056d2876cd00344eb8b94bb7d2
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Wed Jun 3 13:28:07 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jun 3 13:28:07 2020 +0200

    fix build with CONFIG_HYPFS_CONFIG enabled
    
    Commit 58263ed7713e ("xen: add /buildinfo/config entry to hypervisor
    filesystem") added a dependency to .config, but the hypervisor's build
    config could be have another name via setting KCONFIG_CONFIG.
    
    Fix that by using $(KCONFIG_CONFIG) instead. Additionally reference
    the config file via $(XEN_ROOT) instead of a relative path.
    
    Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/common/Makefile b/xen/common/Makefile
index 91581e1815..06881d023c 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -75,7 +75,8 @@ obj-$(CONFIG_UBSAN) += ubsan/
 obj-$(CONFIG_NEEDS_LIBELF) += libelf/
 obj-$(CONFIG_HAS_DEVICE_TREE) += libfdt/
 
-config.gz: ../.config
+CONF_FILE := $(if $(patsubst 
/%,,$(KCONFIG_CONFIG)),$(XEN_ROOT)/xen/)$(KCONFIG_CONFIG)
+config.gz: $(CONF_FILE)
        gzip -c $< >$@
 
 config_data.o: config.gz
--
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