Add a basic TargetARM32 skeleton which knows nothing.

Later commits will add more information, but this tests the
conditional compilation and build setup.

One way to do conditional compilation: determine this
early, at LLVM configure/CMake time. Configure will
fill in the template of SZTargets.def.in to get
a SZTargets.def file.

LLVM change:
https://codereview.chromium.org/1084753002/

NaCl change:
https://codereview.chromium.org/1082953002/

I suppose an alternative is to fill in the .def file via
-D flags in CXXFLAGS.

For conditional lit testing, pnacl-sz dumps the attributes
when given the --build-atts so we just build on top of that.
We do that instead of go the LLVM way of filling in a
lit.site.cfg.in -> lit.site.cfg at configure/CMake time.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4076
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1075363002
diff --git a/src/IceTargetLoweringARM32.def b/src/IceTargetLoweringARM32.def
new file mode 100644
index 0000000..baeec2c
--- /dev/null
+++ b/src/IceTargetLoweringARM32.def
@@ -0,0 +1,20 @@
+//===- subzero/src/IceTargetLoweringARM32.def - ARM32 X-macros --*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines certain patterns for lowering to ARM32 target
+// instructions, in the form of x-macros.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICETARGETLOWERINGARM32_DEF
+#define SUBZERO_SRC_ICETARGETLOWERINGARM32_DEF
+
+// TODO(jvoung): Fill out comparison tables, etc. for 32/64-bit compares.
+
+#endif // SUBZERO_SRC_ICETARGETLOWERINGARM32_DEF