configure.ac: disable annoying warning -Wmissing-field-initializers

It warns for all "{}" initializers.

Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
diff --git a/configure.ac b/configure.ac
index c8c4ace..057a846 100644
--- a/configure.ac
+++ b/configure.ac
@@ -174,7 +174,8 @@
 -Wstrict-aliasing=2 -Winit-self \
 -Wdeclaration-after-statement -Wold-style-definition \
 -Wno-unused-parameter \
--Wno-attributes -Wno-long-long -Winline -Wshadow"
+-Wno-attributes -Wno-long-long -Winline -Wshadow \
+-Wno-missing-field-initializers"
 
 # invalidate cached value if MAYBE_WARN has changed
 if test "x$libdrm_cv_warn_maybe" != "x$MAYBE_WARN"; then