image-postinst-intercepts.bbclass: add class

This class sets POSTINST_INTERCEPTS and POSTINST_INTERCEPTS_CHECKSUMS,
to allow us to pull intercepts from BBPATH. This is kept as a separate
class, as it's needed by both image construction and sdk construction,
the latter to support meta-toolchain & similar recipes.

(From OE-Core rev: 7a2044df4ae8d80cf25a6bfd9b71978ffefbfa33)

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/image-postinst-intercepts.bbclass

@@ -0,0 +1,23 @@
+# Gather existing and candidate postinst intercepts from BBPATH
+POSTINST_INTERCEPTS_DIR ?= "${COREBASE}/scripts/postinst-intercepts"
+POSTINST_INTERCEPTS_PATHS ?= "${@':'.join('%s/postinst-intercepts' % p for p in '${BBPATH}'.split(':'))}:${POSTINST_INTERCEPTS_DIR}"
+
+python find_intercepts() {
+    intercepts = {}
+    search_paths = []
+    paths = d.getVar('POSTINST_INTERCEPTS_PATHS').split(':')
+    overrides = (':' + d.getVar('FILESOVERRIDES')).split(':') + ['']
+    search_paths = [os.path.join(p, op) for p in paths for op in overrides]
+    searched = oe.path.which_wild('*', ':'.join(search_paths), candidates=True)
+    files, chksums = [], []
+    for pathname, candidates in searched:
+        if os.path.isfile(pathname):
+            files.append(pathname)
+            chksums.append('%s:True' % pathname)
+            chksums.extend('%s:False' % c for c in candidates[:-1])
+
+    d.setVar('POSTINST_INTERCEPT_CHECKSUMS', ' '.join(chksums))
+    d.setVar('POSTINST_INTERCEPTS', ' '.join(files))
+}
+find_intercepts[eventmask] += "bb.event.RecipePreFinalise"
+addhandler find_intercepts