toolchain: add PKG_RELEASE if local files

toolchain: add PKG_RELEASE if local files

The toolchain packages partly contain local code like patches and
configuration files. These files are not tracked via PKG_VERSION as this
variable only covers the upstream package version.

To allow versioning of the buildsystem, this commit adds PKG_RELEASE:=1
to all toolchain packages with local files. Whenever a local file is
changed the release must be increased.

This does not touch binutils and gcc for now, as these provide multiple
versions within one package.

Also update the copyright of touched files to 2020.

Signed-off-by: Paul Spooren <mail@aparcar.org>
[exclude binutils/gcc from patch, adjust commit title/message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>