makefile: new qstrip make function

Define a qstrip function that strips double quotes and then
whitespaces around a given string. This is a very commonly needed
thing, and having a function allows to remove a large quantity of
hand-written definitions, followed by a dummy comment to make text
editors not crazy because of the unmatching double quote.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Makefile

@@ -40,6 +40,10 @@ else
 BR2_LOCAL:=$(TOPDIR)/local
 endif
 
+# Strip quotes and then whitespaces
+qstrip=$(strip $(subst ",,$(1)))
+#"))
+
 # Variables for use in Make constructs
 comma:=,
 empty:=