Use 'cc' as default compiler.

Index: make_ffi.py
--- make_ffi.py.orig
+++ make_ffi.py
@@ -77,7 +77,7 @@ def doit(vex_path):
     errs = []
     for cpp in cpplist:
         cmd = [cpp, "-I" + vex_path, os.path.join("pyvex_c", "pyvex.h")]
-        if cpp in ("cl", "clang", "gcc", "cc", "clang++", "g++"):
+        if cpp in ("cc"):
             cmd.append("-E")
         try:
             p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
