selftests: fix ARCH normalization to handle command-line argument

Several selftests Makefiles (e.g.  prctl, breakpoints, etc) attempt to
normalize the ARCH variable by converting x86_64 and i.86 to x86. 
However, it uses the conditional assignment operator '?='.

When ARCH is passed as a command-line argument (e.g., during an rpmbuild
process), the '?=' operator ignores the shell command and the sed
transformation.  This leads to an incorrect ARCH value being used, which
causes build failures

  # make -C tools/testing/selftests TARGETS=prctl ARCH=x86_64
  make: Entering directory '/build/tools/testing/selftests'
  make[1]: Entering directory '/build/tools/testing/selftests/prctl'
  make[1]: *** No targets.  Stop.
  make[1]: Leaving directory '/build/tools/testing/selftests/prctl'
  make: *** [Makefile:197: all] Error 2

Change the assignment to use 'override' and ':=' to ensure the
normalization logic is applied regardless of how the ARCH variable was
initially defined.

Link: https://lkml.kernel.org/r/20260309205145.572778-1-aleksey.oladko@virtuozzo.com
Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Bala-Vignesh-Reddy <reddybalavignesh9979@gmail.com>
Cc: Chelsy Ratnawat <chelsyratnawat2001@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/breakpoints/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Taken from perf makefile
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
 
 TEST_GEN_PROGS := step_after_suspend_test
 

tools/testing/selftests/ipc/Makefile

@@ -1,12 +1,12 @@
 # SPDX-License-Identifier: GPL-2.0
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/i.86/i386/)
 ifeq ($(ARCH),i386)
-        ARCH := x86
+        override ARCH := x86
 	CFLAGS := -DCONFIG_X86_32 -D__i386__
 endif
 ifeq ($(ARCH),x86_64)
-	ARCH := x86
+        override ARCH := x86
 	CFLAGS := -DCONFIG_X86_64 -D__x86_64__
 endif
 

tools/testing/selftests/prctl/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 ifndef CROSS_COMPILE
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
 
 ifeq ($(ARCH),x86)
 TEST_PROGS := disable-tsc-ctxt-sw-stress-test disable-tsc-on-off-stress-test \

tools/testing/selftests/sparc64/Makefile

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/x86_64/x86/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/x86_64/x86/)
 
 ifneq ($(ARCH),sparc64)
 nothing:

tools/testing/selftests/thermal/intel/power_floor/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 ifndef CROSS_COMPILE
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
 
 ifeq ($(ARCH),x86)
 TEST_GEN_PROGS := power_floor_test

tools/testing/selftests/thermal/intel/workload_hint/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 ifndef CROSS_COMPILE
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+override ARCH := $(shell echo $(ARCH) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
 
 ifeq ($(ARCH),x86)
 TEST_GEN_PROGS := workload_hint_test