Fixed clang implicit type cast warning

SConstruct

@@ -1,8 +1,8 @@
-
+# -*- python -*-
+import os
 env = Environment()
 
 env.MergeFlags("-std=gnu99 -Wall -Wextra -Werror -Wno-unused-parameter -Wno-attributes")
-env['MODE'] = 'shared'
 
 AddOption("--variant",
           dest="variant",
@@ -24,9 +24,13 @@ if GetOption("variant") == 'debug':
     env = dbg
 else:
     env = opt
+
+if os.getenv("CC") == "clang":
+    env.Replace(CC="clang",
+                CXX="clang++")
 Export('env')
 
 env.SConscript(["src/SConscript"], variant_dir='build/$VARIANT/src')
 env.SConscript(["examples/SConscript"], variant_dir='build/$VARIANT/examples')
 
-env.Command('test', 'build/$VARIANT/src/test_suite', 'env LD_LIBRARY_PATH=build/$VARIANT/src $SOURCE')
+env.Command('test', 'build/$VARIANT/src/test_suite', 'env LD_LIBRARY_PATH=build/$VARIANT/src $SOURCE')