[bootlin/training-materials] 174a22: yocto: slides: reorganize "Advanced configuration"...

[Luca Ceresoli]

  Branch: refs/heads/master
  Home:   https://github.com/bootlin/training-materials
  Commit: 174a22ce3c44ad3f2cb428f2ae1f09399290a609
      https://github.com/bootlin/training-materials/commit/174a22ce3c44ad3f2cb428f2ae1f09399290a609
  Author: Luca Ceresoli <luca.ceresoli at bootlin.com>
  Date:   2022-08-30 (Tue, 30 Aug 2022)

  Changed paths:
    M slides/yocto-advanced/yocto-advanced.tex
    A slides/yocto-advanced/yocto-operators-order.dia

  Log Message:
  -----------
  yocto: slides: reorganize "Advanced configuration" subsection

- rename subsection to "Variables" as it is all that is about
- move the operators (=, :=, +=, ...) before the overrides, to explain the
  parsing order issue before its solution and also to explain the most
  natural assignment syntax before
- rewrite introductory text accordingly
- reword sentences introducing :append, :prepend and :remove
- convert slide "Operators 2/2" to "Operators caveats"
- separated the modifier overrides (append, prepend, remove) from the
  conditional assignment overrides (OVERRIDES="")
- rewrite examples of machine-based override, mention OVERRIDES variable
- add new picture and explanation at the end about parsing order:
  operators, then :append, then :prepend, then :remove

Signed-off-by: Luca Ceresoli <luca.ceresoli at bootlin.com>