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

.waf-tools/default-compiler-flags.py

@@ -108,6 +108,7 @@ class GccBasicFlags(CompilerFlags):
                               '-Werror',
                               '-Wno-unused-parameter',
                               '-Wno-error=maybe-uninitialized', # Bug #1615
+                              '-Wno-error=deprecated-declarations', # Bug #3795
                               ]
         return flags