build: fix Python 3 unicode issue with waf 1.8.6

Starting with waf 1.8.6 (in Python 3), the hcode variable isn't a
string, but a byte string.

This commit adds the solution proposed in the upstream waf bug report:
https://code.google.com/p/waf/issues/detail?id=1535

It seems a bit overly verbose, but on the other hand, this solution has
the chance of being most correct/compatible.

Fixes #1604.

waftools/waf_customizations.py

@@ -33,7 +33,13 @@ def build(ctx):
 
     cls = Task.classes['cprogram']
     class cprogram(cls):
-        run_str = cls.hcode + '${LAST_LINKFLAGS}'
+        try:
+            run_str = cls.orig_run_str + '${LAST_LINKFLAGS}'
+        except AttributeError:
+            try:
+                run_str = cls.hcode + '${LAST_LINKFLAGS}'
+            except TypeError:
+                run_str = cls.hcode.decode('iso8859-1') + '${LAST_LINKFLAGS}'
 
     cls = Task.classes['macplist']
     class macplist(cls):