kbuild: dummy-tools: avoid tmpdir leak in dummy gcc

commit aac2896 upstream

When passed -print-file-name=plugin, the dummy gcc script creates a
temporary directory that is never cleaned up. To avoid cluttering
$TMPDIR, instead use a static directory included in the source tree.

Fixes: 76426e2 ("kbuild: add dummy toolchains to enable all cc-option etc. in Kconfig")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/9996285f-5a50-e56a-eb1c-645598381a20@kernel.org
[ just the plugin-version.h portion as it failed to apply previously - gregkh ]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>