Improve handling of dynamic library paths on Mac/Windows

SConstruct

@@ -415,7 +415,7 @@ config_options = [
         """Environment variables to propagate through to SCons. Either the
            string 'all' or a comma separated list of variable names, for example,
            'LD_LIBRARY_PATH,HOME'.""",
-        "PATH,LD_LIBRARY_PATH,PYTHONPATH"),
+        "PATH,LD_LIBRARY_PATH,DYLD_LIBRARY_PATH,PYTHONPATH"),
     BoolOption(
         "use_pch",
         "Use a precompiled-header to speed up compilation",

test/SConscript

@@ -45,7 +45,12 @@ localenv.PrependENVPath('PYTHONPATH', Dir('#test/python').abspath)
 PASSED_FILES = {}
 
 # Add build/lib in order to find Cantera shared library
-localenv.PrependENVPath('LD_LIBRARY_PATH', Dir('#build/lib').abspath)
+if env["OS"] == "Windows":
+    localenv.PrependENVPath('PATH', Dir('#build/lib').abspath)
+elif env['OS'] == 'Darwin':
+    localenv.PrependENVPath('DYLD_LIBRARY_PATH', Dir('#build/lib').abspath)
+else:
+    localenv.PrependENVPath('LD_LIBRARY_PATH', Dir('#build/lib').abspath)
 
 def addTestProgram(subdir, progName, env_vars={}):
     """