[XEN PATCH v2 1/5] build: define ARCH and SRCARCH later

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Defining ARCH and SRCARCH later in xen/Makefile allows to switch to
immediate evaluation variable type.

ARCH and SRCARCH depends on value defined in Config.mk and aren't used
TARGET_SUBARCH or TARGET_ARCH, and not before it's needed in a
sub-make or a rule.

This will help reduce the number of times the shell rune is been
run.

With GNU make 4.4, the number of execution of the command present in
these $(shell ) increased greatly. This is probably because as of make
4.4, exported variable are also added to the environment of $(shell )
construct.

Also, `make -d` shows a lot of these:
    Makefile:39: not recursively expanding SRCARCH to export to shell function
    Makefile:38: not recursively expanding ARCH to export to shell function

Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx>
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Tested-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---

Notes:
    v2:
    - change quoting style
    - change identation

 xen/Makefile | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/xen/Makefile b/xen/Makefile
index e89fc461fc..78d176f04e 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -35,12 +35,6 @@ MAKEFLAGS += -rR
 
 EFI_MOUNTPOINT ?= $(BOOT_DIR)/efi
 
-ARCH=$(XEN_TARGET_ARCH)
-SRCARCH=$(shell echo $(ARCH) | \
-          sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g' \
-              -e s'/riscv.*/riscv/g')
-export ARCH SRCARCH
-
 # Allow someone to change their config file
 export KCONFIG_CONFIG ?= .config
 
@@ -241,6 +235,13 @@ include scripts/Kbuild.include
 include $(XEN_ROOT)/Config.mk
 
 # Set ARCH/SUBARCH appropriately.
+
+ARCH := $(XEN_TARGET_ARCH)
+SRCARCH := $(shell echo $(ARCH) | \
+    sed -e 's/x86.*/x86/' -e 's/arm\(32\|64\)/arm/g' \
+        -e 's/riscv.*/riscv/g')
+export ARCH SRCARCH
+
 export TARGET_SUBARCH  := $(XEN_TARGET_ARCH)
 export TARGET_ARCH     := $(shell echo $(XEN_TARGET_ARCH) | \
                             sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g' \
-- 
Anthony PERARD