[PATCH v2 1/4] build: add make macro for making file from file.in

[Juergen Gross <jgross@suse.com>]

Add a new make macro for creating <file> from <file>.in at build
time. To be used like this:

$(foreach file,$(IN_FILES),$(eval $(call apply-build-vars,$(file))))

This can be used instead of the current approach to perform the similar
step for file.in during ./configure.

This will avoid having to run ./configure just because of modifying a
file depending on a variable set by configure.

Prepare to have multiple files as source for the replacement patterns.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- don't use pattern rule, but create explicit dependency in macro,
  don't require to rename source files (Jan Beulich, Andrew Cooper)
---
 Config.mk | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Config.mk b/Config.mk
index e1556dfbfa..d21d67945a 100644
--- a/Config.mk
+++ b/Config.mk
@@ -159,6 +159,19 @@ define move-if-changed
 	if ! cmp -s $(1) $(2); then mv -f $(1) $(2); else rm -f $(1); fi
 endef
 
+PATH_FILES := Paths
+INC_FILES := $(foreach f, $(PATH_FILES), $(XEN_ROOT)/config/$(f).mk)
+
+include $(INC_FILES)
+
+BUILD_MAKE_VARS := $(foreach f, $(PATH_FILES), $(shell awk '$$2 == ":=" { print $$1; }' $(XEN_ROOT)/config/$(f).mk.in))
+
+# Replace @xxx@ markers in $(1).in with $(xxx) variable contents, write to $(1)
+define apply-build-vars
+ $(1): $(1).in
+	sed $$(foreach v, $$(BUILD_MAKE_VARS), -e 's#@$$(v)@#$$($$(v))#g') <$$< >$$@
+endef
+
 CFLAGS += -fno-strict-aliasing
 
 CFLAGS += -std=gnu99
-- 
2.51.0