File compiler_error_nonnull.patch of Package casync

--- casync-2/meson.build	2017-07-26 11:55:38.000000000 +0200
+++ casync-2/meson.build	2017-09-17 14:24:41.820171774 +0200
@@ -53,6 +53,7 @@
         -fstack-protector-strong
         -fPIE
         --param=ssp-buffer-size=4
+        -Wno-nonnull
 '''.split()
 
 foreach arg : c_args