build: downgrade maybe-uninitialized from an error to a warning

maybe-uninitialized has false positives in gcc 4.8 due to
Boost ticket #9134 https://svn.boost.org/trac/boost/ticket/9134

refs #1560

Change-Id: I44e2456b31f3a102d4a447da0dc81c23efb31f3b
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index 741791e..0df0347 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -30,7 +30,8 @@
                          '-g3',
                          '-fcolor-diagnostics', # clang
                          '-fdiagnostics-color', # gcc >= 4.9
-                         '-Werror'
+                         '-Werror',
+                         '-Wno-error=maybe-uninitialized', # Bug #1560
                         ]
         if areCustomCxxflagsPresent:
             missingFlags = [x for x in defaultFlags if x not in conf.env.CXXFLAGS]