[Buildroot] [PATCH 0 of 2 v4-resend] Add find utility functions / exclude files from strip

[Thomas De Schampheleire <patrickdepinguin+buildroot@gmail.com>]

This patch series adds a few utility functions to Makefile.package.in that
help in composing find commands, and uses these functions to exclude
user-configured files and directories from being stripped in target-finalize.

Thanks to input from Arnout, the find functions are now much simpler and
should be clearly understandable by everyone.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

---
v4: simplify find functions even further; whitespace changes
v3: update based on review comments, remove Python changes for now
v2: simplify find functions

 Config.in                   |  19 +++++++++++++++++++
 Makefile                    |  10 ++++++++--
 package/Makefile.package.in |  10 ++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)