SCons: Fix checks for clang in env['CXX']

They would match the whole path instead of only the filename.

platform/server/detect.py

@@ -56,7 +56,7 @@ def configure(env):
     ## Compiler configuration
 
     if env['use_llvm']:
-        if ('clang++' not in env['CXX']):
+        if ('clang++' not in os.path.basename(env['CXX'])):
             env["CC"] = "clang"
             env["CXX"] = "clang++"
             env["LINK"] = "clang++"