examples: make examples/ optional

Most users don't need the standalone API examples. Distributions like SUSE
do not supply libgcc for cross-compiling and we cannot do without on ARMv8
for building examples/.

Make examples selectable via symbol CONFIG_EXAMPLES. It defaults to
yes on ARCH_QEMU to ensure that we compile the API as part of our
continuous integration.

Cc: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NTom Rini <trini@konsulko.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NMatthias Brugger <mbrugger@suse.com>

Kconfig

@@ -422,6 +422,14 @@ config SYS_SRAM_SIZE
 	default 0x10000 if TARGET_TRICORDER
 	default 0x0
 
+config EXAMPLES
+	bool "Compile API examples"
+	depends on !SANDBOX
+	default y if ARCH_QEMU
+	help
+	  U-Boot provides an API for standalone applications. Examples are
+	  provided in directory examples/.
+
 endmenu		# General setup
 
 menu "Boot images"

examples/Makefile

 # SPDX-License-Identifier: GPL-2.0+
 
-ifndef CONFIG_SANDBOX
+ifdef CONFIG_EXAMPLES
 
 ifdef FTRACE
 subdir-ccflags-y += -finstrument-functions -DFTRACE