support/scripts/get-developers: add new script

support/scripts/get-developers: add new script

This script, and its companion library, is more-or-less Buildroot's
equivalent to the kernel get_maintainer.pl script: it allows to get the
list of developers to whom a set of patches should be sent to.

To do so, it first relies on a text file, named DEVELOPERS, at the root
of the Buildroot source tree (added in a followup commit) to list the
developers and the files they are interested in. The DEVELOPERS file's
format is simple:

N:     Firstname Lastname <email>
F:     path/to/file
F:     path/to/another/file

This allows to associate developers with the files they are looking
after, be they related to a package, a defconfig, a filesystem image, a
package infrastructure, the documentation, or anything else.

When a directory is given, the tool assumes that the developer handles
all files and subdirectories in this directory. For example
"package/qt5/" can be used for the developers looking after all the Qt5
packages.

Conventional shell patterns can be used, so "package/python-*" can be
used for the developers who want to look after all packages matching
"python-*".

A few files are recognized specially:

 - .mk files are parsed, and if they contain $(eval
   $(<something>-package)), the developer is assumed to be looking after
   the corresponding package. This way, autobuilder failures for this
   package can be reported directly to this developer.

 - arch/Config.in.<arch> files are recognized as "the developer is
   looking after the <arch> architecture". In this case, get-developer
   parses the arch/Config.in.<arch> to get the list of possible BR2_ARCH
   values. This way, autobuilder failures for this package can be
   reported directly to this developer.

 - pkg/pkg-<infra>.mk are recognized as "the developer is looking after
   the <infra> package infrastructure. In this case, any patch that adds
   or touches a .mk file that uses this infrastructure will be sent to
   this developer.

Examples of usage:

$ ./support/scripts/get-developers 0001-ffmpeg-fix-bfin-build.patch
git send-email--to buildroot@buildroot.org --to "Luca Ceresoli <luca@lucaceresoli.net>" --to "Bernd Kuhls <bernd.kuhls@t-online.de>"

$ ./support/scripts/get-developers -p imx-lib
Arnout Vandecappelle <arnout@mind.be>
Gary Bisson <gary.bisson@boundarydevices.com>

$ ./support/scripts/get-developers -a bfin
Waldemar Brodkorb <wbx@openadk.org>

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>