[xen staging] build: use if_changed_rule with %.o:%.c targets

[patchbot@xxxxxxx]

commit 332c735d24387152e8f578e38066b5d03803c2a2
Author:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Tue Sep 7 09:16:45 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Sep 7 09:16:45 2021 +0200

    build: use if_changed_rule with %.o:%.c targets
    
    Use $(dot-target) to have the target name prefix with a dot.
    
    Now, when the CC command has run, it is recorded in .*.cmd
    file, then if_changed_rules will compare it on subsequent runs.
    
    Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/Rules.mk | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index a715a4525e..11c253026b 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -192,19 +192,27 @@ FORCE:
 
 SRCPATH := $(patsubst $(BASEDIR)/%,%,$(CURDIR))
 
-%.o: %.c Makefile
+quiet_cmd_cc_o_c = CC      $@
 ifeq ($(CONFIG_ENFORCE_UNIQUE_SYMBOLS),y)
-       $(CC) $(c_flags) -c $< -o $(@D)/.$(@F).tmp -MQ $@
-ifeq ($(CONFIG_CC_IS_CLANG),y)
-       $(OBJCOPY) --redefine-sym $<=$(SRCPATH)/$< $(@D)/.$(@F).tmp $@
-else
-       $(OBJCOPY) --redefine-sym $(<F)=$(SRCPATH)/$< $(@D)/.$(@F).tmp $@
-endif
-       rm -f $(@D)/.$(@F).tmp
+    cmd_cc_o_c = $(CC) $(c_flags) -c $< -o $(dot-target).tmp -MQ $@
+    ifeq ($(CONFIG_CC_IS_CLANG),y)
+        cmd_objcopy_fix_sym = $(OBJCOPY) --redefine-sym $<=$(SRCPATH)/$< 
$(dot-target).tmp $@
+    else
+        cmd_objcopy_fix_sym = $(OBJCOPY) --redefine-sym $(<F)=$(SRCPATH)/$< 
$(dot-target).tmp $@
+    endif
+    cmd_objcopy_fix_sym += && rm -f $(dot-target).tmp
 else
-       $(CC) $(c_flags) -c $< -o $@
+    cmd_cc_o_c = $(CC) $(c_flags) -c $< -o $@
 endif
 
+define rule_cc_o_c
+    $(call cmd_and_record,cc_o_c)
+    $(call cmd,objcopy_fix_sym)
+endef
+
+%.o: %.c FORCE
+       $(call if_changed_rule,cc_o_c)
+
 quiet_cmd_cc_o_S = CC      $@
 cmd_cc_o_S = $(CC) $(a_flags) -c $< -o $@
 
--
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