Unbreak 'make tools/*' for user-space targets

Unbreak 'make tools/*' for user-space targets

This pattern isn't very documented, and apparently not used much outside
of 'make tools/help', but it has existed for over a decade (since commit
ea01fa9f63ae: "tools: Connect to the kernel build system").

However, it doesn't work very well for most cases, particularly the
useful "tools/all" target, because it overrides the LDFLAGS value with
an empty one.

And once overridden, 'make' will then not honor the tooling makefiles
trying to change it - which then makes any LDFLAGS use in the tooling
directory break, typically causing odd link errors.

Remove that LDFLAGS override, since it seems to be entirely historical.
The core kernel makefiles no longer modify LDFLAGS as part of the build,
and use kernel-specific link flags instead (eg 'KBUILD_LDFLAGS' and
friends).

This allows more of the 'make tools/*' cases to work.  I say 'more',
because some of the tooling build rules make various other assumptions
or have other issues, so it's still a bit hit-or-miss.  But those issues
tend to show up with the 'make -C tools xyz' pattern too, so now it's no
longer an issue of this particular 'tools/*' build rule being special.

Acked-by: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>