The current mechanism uses a completely separate build rule for each
file which must be built with system headers. This is tricky to
maintain.

Add a foreach template in the sandbox cpu Makefile which generates the
custom compile rules from a CFLAGS_USE_SYSHDRS list. This keeps the
rules data-driven without needing changes to the common
scripts/Makefile.lib, which could affect other architectures.

Move initjmp.o into the template since it uses the same pattern. Add
sdl.o to the list too, with an override for its command since it also
needs -fshort-wchar removed and -fno-lto added.

Signed-off-by: Simon Glass <sjg@chromium.org>

sdl.c is compiled against the SDL library.

Trying to redefine wchar_t with -fshort-wchar is not necessary
and leads to build failures when compiling against musl.

Cc: Milan P. Stanić <mps@arvanta.net>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

At present sandbox has a start.o in the 'start' target but also includes
it in the normal target list. This is not how this is normally handled. It
is needed because sandbox does not include the u-boot-init variable in its
link rule.

Update the rule and move start.o from the normal target list to the
'extras' list.

Signed-off-by: Simon Glass <sjg@chromium.org>

When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from.  So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry.  Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.

In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.

This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents.  There's also a few places where I found we did not have a tag
and have introduced one.

Signed-off-by: Tom Rini <trini@konsulko.com>

Introduce a Makefile under arch/$ARCH/ and include it in the
top Makefile (similar to Linux kernel). This allows further
refactoringi like moving architecture-specific code out of global
makefiles, deprecating config variables (CPU, CPUDIR, SOC) or
deprecating arch/$ARCH/config.mk.

In contrary to Linux kernel, U-Boot defines the ARCH variable by
Kconfig, thus the arch Makefile can only included conditionally
after the top config.mk.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Acked-by: Masahiro Yamada <yamada.m@jp.panasonic.com>