configure: Add -Wno-format-zero-length to CFLAGS.

The C standard specifies that zero-length format strings are allowed.

diff --git a/configure b/configure
index f557482..e20bb06 100755 (executable)
--- a/configure
+++ b/configure
@@ -2978,6 +2978,7 @@ check_cflags -Wdeclaration-after-statement
 check_cflags -Wall
 check_cflags -Wno-parentheses
 check_cflags -Wno-switch
+check_cflags -Wno-format-zero-length
 check_cflags -Wdisabled-optimization
 check_cflags -Wpointer-arith
 check_cflags -Wredundant-decls