ref-manual, dev-manual, bsp-guide: Applied Paul Eggleton Build history patch 4 of 5.

* BBFILES should be appended to with +=

* BBPATH should be appended to with .=

* Immediate expansion is not necessary for BBFILE_PRIORITY

* Immediate expansion is not necessary for references in layer.conf
  to LAYERDIR since these are automatically expanded at the end of
  parsing the file (and have been for some time).

* Add collection name override to BBFILE_PRIORITY example

* Fix comments referring to old structure ("packages directory" or
  "recipes directory")

(From yocto-docs rev: 0aaac8f5ad97c802ebe1d4f3ffb7987050533292)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/bsp-guide/bsp.xml

@@ -312,14 +312,14 @@
             <para>
                <literallayout class='monospaced'>
      # We have a conf and classes directory, add to BBPATH
-     BBPATH := "${BBPATH}:${LAYERDIR}"
+     BBPATH .= ":${LAYERDIR}"
 
-     # We have a recipes directory, add to BBFILES
-     BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*.bb \
+     # We have recipes-* directories, add to BBFILES
+     BBFILES += "${LAYERDIR}/recipes-*/*.bb \
                  ${LAYERDIR}/recipes-*/*.bbappend"
 
      BBFILE_COLLECTIONS += "bsp"
-     BBFILE_PATTERN_bsp := "^${LAYERDIR}/"
+     BBFILE_PATTERN_bsp = "^${LAYERDIR}/"
      BBFILE_PRIORITY_bsp = "6"
                 </literallayout>
             </para>
@@ -329,7 +329,7 @@
                 Bay <filename>conf/layer.conf</filename> file:
                <literallayout class='monospaced'>
      BBFILE_COLLECTIONS += "crownbay"
-     BBFILE_PATTERN_crownbay := "^${LAYERDIR}/"
+     BBFILE_PATTERN_crownbay = "^${LAYERDIR}/"
      BBFILE_PRIORITY_crownbay = "6"
                 </literallayout>
             </para>