Merge "Fix "_FORTIFY_SOURCE" redefined warning" into experimental

build/make/configure.sh

diff --git a/build/make/configure.sh b/build/make/configure.sh
index 9bff9cb..00c27c2 100755
--- a/build/make/configure.sh
+++ b/build/make/configure.sh
@@ -974,7 +974,7 @@
 
     # Work around longjmp interception on glibc >= 2.11, to improve binary
     # compatibility. See http://code.google.com/p/webm/issues/detail?id=166
-    enabled linux && check_add_cflags -D_FORTIFY_SOURCE=0
+    enabled linux && check_add_cflags -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0
 
     # Check for strip utility variant
     ${STRIP} -V 2>/dev/null | grep GNU >/dev/null && enable gnu_strip