build: add waf-tool to simplify building with AddressSanitizer & friends

Change-Id: If36e52f5e49d94ad5846165c50504d06d7d3c4d0
Refs: #2589
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index 07f1feb..28da538 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -60,7 +60,7 @@
             supportedFlags += [flag]
 
     self.end_msg(' '.join(supportedFlags))
-    self.env.CXXFLAGS = supportedFlags + self.env.CXXFLAGS
+    self.env.prepend_value('CXXFLAGS', supportedFlags)
 
 @Configure.conf
 def add_supported_linkflags(self, linkflags):
@@ -78,7 +78,7 @@
             supportedFlags += [flag]
 
     self.end_msg(' '.join(supportedFlags))
-    self.env.LINKFLAGS = supportedFlags + self.env.LINKFLAGS
+    self.env.prepend_value('LINKFLAGS', supportedFlags)
 
 
 class CompilerFlags(object):