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-rw-r--r--Makefile.inc21
1 files changed, 17 insertions, 4 deletions
diff --git a/Makefile.inc b/Makefile.inc
index 7ce236031e..3840505cd5 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -464,11 +464,24 @@ export $(COREBOOT_EXPORTS)
#######################################################################
# generate build support files
-$(obj)/build.h: .xcompile
+
+build_h := $(obj)/build.h
+
+# We have to manually export variables that `genbuild_h.sh` uses
+# when we call it through the `$(shell)` function. This is fragile
+# but as variables newly added to `genbuild_h.sh` would just not
+# work, we'd notice that instantly at least.
+build_h_exports := BUILD_TIMELESS KERNELVERSION COREBOOT_EXTRA_VERSION
+
+# Report new `build.ht` as dependency if `build.h` differs.
+build_h_check := \
+ export $(foreach exp,$(build_h_exports),$(exp)="$($(exp))"); \
+ util/genbuild_h/genbuild_h.sh >$(build_h)t 2>/dev/null; \
+ cmp -s $(build_h)t $(build_h) >/dev/null 2>&1 || echo $(build_h)t
+
+$(build_h): $$(shell $$(build_h_check))
@printf " GEN build.h\n"
- rm -f $(obj)/build.h
- util/genbuild_h/genbuild_h.sh > $(obj)/build.ht
- mv $(obj)/build.ht $(obj)/build.h
+ mv $< $@
build-dirs:
mkdir -p $(objcbfs) $(objgenerated)