[geary] Suppress some C compiler build warnings.

[Michael Gratton <mjog src gnome org>]

commit dfd3355d4862047bb10ef4457f4e8c43f2fa7795
Author: Michael James Gratton <mike vee net>
Date:   Mon Oct 16 09:26:33 2017 +1030

    Suppress some C compiler build warnings.
    
    Vala causes a _lot_ of these to be emitted for otherwise valid
    code. Suppress them so we can actually see more useful warnings.
    
    * src/CMakeLists.txt: Suppress incompatible-pointer-types and
      discarded-qualifiers C compiler warnings.

 src/CMakeLists.txt |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4e8a0c4..bb56e06 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -575,6 +575,10 @@ set(CFLAGS
     -DISO_CODE_639_XML=\"${ISO_CODE_639_XML}\"
     -DISO_CODE_3166_XML=\"${ISO_CODE_3166_XML}\"
     -DGCR_API_SUBJECT_TO_CHANGE
+    # Vala causes a _lot_ of these to be emitted for otherwise valid
+    # code. Suppress them so we can actually see more useful warnings.
+    -Wno-incompatible-pointer-types
+    -Wno-discarded-qualifiers
 )
 
 if (REF_TRACKING)