build: update waf to version 2.0.27

Change-Id: I6a35992c1c9a5dd30b6e04a8993edfafb7f358fa
diff --git a/.waf-tools/boost.py b/.waf-tools/boost.py
index a6cdabe..dab6949 100644
--- a/.waf-tools/boost.py
+++ b/.waf-tools/boost.py
@@ -1,6 +1,3 @@
-#!/usr/bin/env python
-# encoding: utf-8
-#
 # partially based on boost.py written by Gernot Vormayr
 # written by Ruediger Sonderfeld <ruediger@c-plusplus.de>, 2008
 # modified by Bjoern Michaelsen, 2008
diff --git a/.waf-tools/coverage.py b/.waf-tools/coverage.py
index cc58165..4ca9740 100644
--- a/.waf-tools/coverage.py
+++ b/.waf-tools/coverage.py
@@ -1,5 +1,3 @@
-# -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
-
 from waflib import TaskGen
 
 def options(opt):
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index 6869097..39b3025 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -1,5 +1,3 @@
-# -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
-
 import platform
 from waflib import Configure, Logs, Utils
 
@@ -128,16 +126,16 @@
 
     def getGeneralFlags(self, conf):
         """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are always needed"""
+        return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': []}
+
+    def getDebugFlags(self, conf):
+        """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are needed only in debug mode"""
         return {
             'CXXFLAGS': [],
             'LINKFLAGS': [],
             'DEFINES': ['BOOST_ASIO_NO_DEPRECATED', 'BOOST_FILESYSTEM_NO_DEPRECATED'],
         }
 
-    def getDebugFlags(self, conf):
-        """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are needed only in debug mode"""
-        return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': []}
-
     def getOptimizedFlags(self, conf):
         """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are needed only in optimized mode"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': ['NDEBUG']}
@@ -246,6 +244,9 @@
         elif self.getCompilerVersion(conf) >= (15, 0, 0):
             # https://releases.llvm.org/15.0.0/projects/libcxx/docs/UsingLibcxx.html#enabling-the-safe-libc-mode
             flags['DEFINES'] += ['_LIBCPP_ENABLE_ASSERTIONS=1']
+        # Tell libc++ to avoid including transitive headers
+        # https://libcxx.llvm.org/DesignDocs/HeaderRemovalPolicy.html
+        flags['DEFINES'] += ['_LIBCPP_REMOVE_TRANSITIVE_INCLUDES=1']
         return flags
 
     def getOptimizedFlags(self, conf):
diff --git a/.waf-tools/openssl.py b/.waf-tools/openssl.py
index 51521c4..07c3c6a 100644
--- a/.waf-tools/openssl.py
+++ b/.waf-tools/openssl.py
@@ -1,6 +1,3 @@
-#! /usr/bin/env python
-# encoding: utf-8
-
 """
 When using this tool, the wscript should look like:
 
diff --git a/.waf-tools/sanitizers.py b/.waf-tools/sanitizers.py
index a8fe55d..c65d009 100644
--- a/.waf-tools/sanitizers.py
+++ b/.waf-tools/sanitizers.py
@@ -1,4 +1,4 @@
-# -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
+# Davide Pesavento (LIP6), 2016
 
 def options(opt):
     opt.add_option('--with-sanitizer', action='store', default='', dest='sanitizers',
diff --git a/.waf-tools/sqlite3.py b/.waf-tools/sqlite3.py
index 4f2c016..66fb945 100644
--- a/.waf-tools/sqlite3.py
+++ b/.waf-tools/sqlite3.py
@@ -1,6 +1,3 @@
-#! /usr/bin/env python
-# encoding: utf-8
-
 from waflib.Configure import conf
 
 def options(opt):