Although not specific to buildroot, I am not sure this is the best
way to handle user-supplied CFLAGS.
-diff -durN dtc-e4b497f367a3b2ae99cc52089a14a221b13a76ef.orig/Makefile dtc-e4b497f367a3b2ae99cc52089a14a221b13a76ef/Makefile
---- dtc-e4b497f367a3b2ae99cc52089a14a221b13a76ef.orig/Makefile 2012-10-22 22:02:47.541240846 +0200
-+++ dtc-e4b497f367a3b2ae99cc52089a14a221b13a76ef/Makefile 2012-10-22 22:03:21.151047833 +0200
-@@ -18,7 +18,8 @@
+diff --git a/Makefile b/Makefile
+index 962f94eba661..bf6b317158cf 100644
+--- a/Makefile
++++ b/Makefile
+@@ -16,9 +16,10 @@ LOCAL_VERSION =
+ CONFIG_LOCALVERSION =
+
CPPFLAGS = -I libfdt -I .
- WARNINGS = -Werror -Wall -Wpointer-arith -Wcast-qual -Wnested-externs \
+-WARNINGS = -Werror -Wall -Wpointer-arith -Wcast-qual -Wnested-externs \
++WARNINGS = -Wall -Wpointer-arith -Wcast-qual -Wnested-externs \
-Wstrict-prototypes -Wmissing-prototypes -Wredundant-decls
-CFLAGS = -g -Os -fPIC -Werror $(WARNINGS)
+CFLAGS ?= -g -Os