binman: Support cross-compiling test files to x86

These test files are currently "intended for use on x86 hosts", but most
of the tests using them can still pass when cross-compiled to x86 on an
arm64 host.

This patch enables non-x86 hosts to run the tests by specifying a
cross-compiler via CROSS_COMPILE. The list of variables it sets is taken
from the top-level Makefile. It would be possible to automatically set
an x86 cross-compiler with a few blocks like:

    ifneq ($(shell i386-linux-gnu-gcc --version 2> /dev/null),)
    CROSS_COMPILE = i386-linux-gnu-
    endif

But it wouldn't propagate to the binman process calling this Makefile,
so it's better just raise an error and expect 'binman test' to be run
with a correct CROSS_COMPILE.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/binman/test/Makefile

@@ -7,6 +7,19 @@
 # SPDX-License-Identifier:      GPL-2.0+
 #
 
+HOSTARCH := $(shell uname -m | sed -e s/i.86/x86/ )
+ifeq ($(findstring $(HOSTARCH),"x86" "x86_64"),)
+ifeq ($(findstring $(MAKECMDGOALS),"help" "clean"),)
+ifndef CROSS_COMPILE
+$(error Binman tests need to compile to x86, but the CPU arch of your \
+	machine is $(HOSTARCH). Set CROSS_COMPILE to a suitable cross compiler)
+endif
+endif
+endif
+
+CC		= $(CROSS_COMPILE)gcc
+OBJCOPY		= $(CROSS_COMPILE)objcopy
+
 VPATH := $(SRC)
 CFLAGS := -march=i386 -m32 -nostdlib -I $(SRC)../../../include \
 	-Wl,--no-dynamic-linker
@@ -32,7 +45,7 @@ bss_data: CFLAGS += $(SRC)bss_data.lds
 bss_data: bss_data.c
 
 u_boot_binman_syms.bin: u_boot_binman_syms
-	objcopy -O binary $< -R .note.gnu.build-id $@
+	$(OBJCOPY) -O binary $< -R .note.gnu.build-id $@
 
 u_boot_binman_syms: CFLAGS += $(LDS_BINMAN)
 u_boot_binman_syms: u_boot_binman_syms.c