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

Change-Id: I368fe5bbbe3a92a7e82c22f56f6784761d94118d
Refs: #2589
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index abe0a25..fd15dbb 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):