[xen stable-4.17] Config.mk: evaluate XEN_COMPILE_ARCH and XEN_OS immediately

[patchbot@xxxxxxx]

commit 476d2624ec3cf3e60709580ff1df208bb8f616e2
Author:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Mon Jul 31 15:02:34 2023 +0200
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Aug 22 13:43:05 2023 +0100

    Config.mk: evaluate XEN_COMPILE_ARCH and XEN_OS immediately
    
    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.
    
    So to avoid having these command been run more than necessary, we
    will replace ?= by an equivalent but with immediate expansion.
    
    Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Tested-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit a07414d989cf52e5e84192b78023bee1589bbda4)
---
 Config.mk | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Config.mk b/Config.mk
index 8bc2bcd5f6..4864033c73 100644
--- a/Config.mk
+++ b/Config.mk
@@ -19,13 +19,17 @@ or       = $(if $(strip $(1)),$(1),$(if $(strip 
$(2)),$(2),$(if $(strip $(3)),$(
 
 -include $(XEN_ROOT)/.config
 
-XEN_COMPILE_ARCH    ?= $(shell uname -m | sed -e s/i.86/x86_32/ \
+ifeq ($(origin XEN_COMPILE_ARCH), undefined)
+XEN_COMPILE_ARCH    := $(shell uname -m | sed -e s/i.86/x86_32/ \
                          -e s/i86pc/x86_32/ -e s/amd64/x86_64/ \
                          -e s/armv7.*/arm32/ -e s/armv8.*/arm64/ \
                          -e s/aarch64/arm64/)
+endif
 
 XEN_TARGET_ARCH     ?= $(XEN_COMPILE_ARCH)
-XEN_OS              ?= $(shell uname -s)
+ifeq ($(origin XEN_OS), undefined)
+XEN_OS              := $(shell uname -s)
+endif
 
 CONFIG_$(XEN_OS) := y
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.17