Make it possible to pass LLVM options from environment variables.

These options are parsed like commandline options to llc.

test/native_asm.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+
+from llvm import *
+from llvm.core import *
+import sys, os
+import unittest
+
+class TestNativeAsm(unittest.TestCase):
+    def test_asm(self):
+        # create a module
+        m = Module.new('module1')
+
+        foo = m.add_function(Type.function(Type.int(), [Type.int(), Type.int()]), name="foo")
+
+        bldr = Builder.new(foo.append_basic_block('entry'))
+        x = bldr.add(foo.args[0], foo.args[1])
+        bldr.ret(x)
+
+        att_syntax = m.to_native_assembly()
+        os.environ["LLVMPY_OPTIONS"] = "-x86-asm-syntax=intel"
+        parse_environment_options(sys.argv[0], "LLVMPY_OPTIONS")
+        intel_syntax = m.to_native_assembly()
+
+        print(att_syntax)
+        print(intel_syntax)
+        self.assertNotEqual(att_syntax, intel_syntax)
+
+if __name__ == '__main__':
+    unittest.main()