build: require gcc >= 5.3 and switch to C++14

Change-Id: Iba0a1fc8e4a0a0d5ec4150d4dca96792a73237e3
Refs: #3076, #4462
diff --git a/wscript b/wscript
index 1b44ea8..20dcad5 100644
--- a/wscript
+++ b/wscript
@@ -157,7 +157,7 @@
             else:
                 # no tags matched
                 Context.g_module.VERSION = '%s-commit-%s' % (VERSION_BASE, out)
-    except subprocess.CalledProcessError:
+    except (OSError, subprocess.CalledProcessError):
         pass
 
     versionFile = ctx.path.find_node('VERSION')