Makefile: use STRIP_ARGS = -s on all systems

Set -s (--strip-all) as STRIP_ARGS explicitly on all systems instead of
only on systems (SunOS / Solaris) where strip-all is not the default
behavior.

Change-Id: I2c80d553fb54d94bc65f07e700c90dd1bae4854e
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.de>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/58246
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72238
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile b/Makefile
index 96ecb29..36c0896 100644
--- a/Makefile
+++ b/Makefile
@@ -28,6 +28,7 @@
 # Note for anyone editing this Makefile: gnumake will happily ignore any
 # changes in this Makefile to variables set on the command line.
 STRIP   ?= strip
+STRIP_ARGS = -s
 INSTALL = install
 DIFF    = diff
 PREFIX  ?= /usr/local
@@ -159,10 +160,6 @@
 CC = gcc
 endif
 
-ifneq ($(HOST_OS), SunOS)
-STRIP_ARGS = -s
-endif
-
 # Determine the destination OS.
 # IMPORTANT: The following line must be placed before TARGET_OS is ever used
 # (of course), but should come after any lines setting CC because the line