[XEN PATCH v6 16/31] build: avoid building arm/arm/*/head.o twice

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

head.o is been built twice, once because it is in $(ALL_OBJS) and a
second time because it is in $(extra-y) and thus it is rebuilt when
building "arch/arm/built_in.o".

Fix this by adding a dependency of "head.o" on the directory
"arch/arm/".

Also, we should avoid building object that are in subdirectories, so
move the declaration in there. This doesn't change anything as
"arch/arm/built_in.o" depends on "arch/arm/$subarch/built_in.o" which
depends on $(extra-y), so we still need to depend on
"arch/arm/built_in.o".

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 xen/arch/arm/Makefile       | 7 ++++++-
 xen/arch/arm/arm32/Makefile | 1 +
 xen/arch/arm/arm64/Makefile | 2 ++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 3d0af8ebc93c..cc90d9796e6e 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -64,7 +64,6 @@ obj-$(CONFIG_SBSA_VUART_CONSOLE) += vpl011.o
 obj-y += vsmc.o
 obj-y += vpsci.o
 obj-y += vuart.o
-extra-y += $(TARGET_SUBARCH)/head.o
 
 extra-y += xen.lds
 
@@ -76,6 +75,12 @@ endif
 
 ALL_OBJS := $(TARGET_SUBARCH)/head.o $(ALL_OBJS)
 
+# head.o is built by descending into the sub-directory, depends on the part of
+# $(ALL_OBJS) that will eventually recurse into $(TARGET_SUBARCH)/ and build
+# head.o
+$(TARGET_SUBARCH)/head.o: $(BASEDIR)/arch/arm/built_in.o
+$(TARGET_SUBARCH)/head.o: ;
+
 ifdef CONFIG_LIVEPATCH
 all_symbols = --all-symbols
 ifdef CONFIG_FAST_SYMBOL_LOOKUP
diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
index 96105d238307..3040eabce3ad 100644
--- a/xen/arch/arm/arm32/Makefile
+++ b/xen/arch/arm/arm32/Makefile
@@ -11,3 +11,4 @@ obj-y += smpboot.o
 obj-y += traps.o
 obj-y += vfp.o
 
+extra-y += head.o
diff --git a/xen/arch/arm/arm64/Makefile b/xen/arch/arm/arm64/Makefile
index 40642ff57494..0bb284dedab2 100644
--- a/xen/arch/arm/arm64/Makefile
+++ b/xen/arch/arm/arm64/Makefile
@@ -13,3 +13,5 @@ obj-y += smpboot.o
 obj-y += traps.o
 obj-y += vfp.o
 obj-y += vsysreg.o
+
+extra-y += head.o
-- 
Anthony PERARD