build: Do not fail the build in debug mode when using deprecated declarations

The original motivation of this change was to avoid compilation failure
in debug mode on macOS 10.12.

Change-Id: I15437050555646b2458989f3788fce4c1e354e48
Refs: #3795
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index fd15dbb..2999e8f 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -108,6 +108,7 @@
                               '-Werror',
                               '-Wno-unused-parameter',
                               '-Wno-error=maybe-uninitialized', # Bug #1615
+                              '-Wno-error=deprecated-declarations', # Bug #3795
                               ]
         return flags