Revert "Enforce python2 for systems that use python3 as their default."

This reverts commit r200413.

This was breaking the build on systems where the python 2.x executable
was called python.

llvm-svn: 201239

libclc/configure.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/python
 
 def c_compiler_rule(b, name, description, compiler, flags):
   command = "%s -MMD -MF $out.d %s -c -o $out $in" % (compiler, flags)