[Buildroot] [PATCH 01 of 20] pkg-generic: introduce helper function to check for a deprecated variable

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

This patch introduces a helper check-deprecated-variable, that throws an
error when a package defines a deprecated variable. This helps in detecting
transition errors when changing the buildroot infrastructures, and also
helps users that have created packages not part of mainline buildroot.

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

---
 package/pkg-generic.mk |  15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff -r 6ff0cfa8a802 -r 677354152366 package/pkg-generic.mk
--- a/package/pkg-generic.mk	Tue May 20 13:53:00 2014 +1200
+++ b/package/pkg-generic.mk	Mon Jul 28 21:39:53 2014 +0200
@@ -264,6 +264,21 @@
 endef
 
 ################################################################################
+# check-deprecated-variable -- throw an error on deprecated variables
+#
+# argument 1 is the deprecated variable
+# argument 2 is the new variable to use
+#
+# example:
+#   $(eval $(call check-deprecated-variable,FOO_MAKE_OPT,FOO_MAKE_OPTS))
+################################################################################
+define check-deprecated-variable
+ifneq ($$(origin $(1)),undefined)
+$$(error Package error: use $(2) instead of $(1). Please fix your .mk file)
+endif
+endef
+
+################################################################################
 # inner-generic-package -- generates the make targets needed to build a
 # generic package
 #