Initial import of cast-0.2.3.

Bug: 155309706
Change-Id: Ie467335fa7d10dc1ac9e0083a27bfd1a057e9c69
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..2aa9f5b
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,8 @@
+extern crate rustc_version;
+
+fn main() {
+    let vers = rustc_version::version().unwrap();
+    if vers.major == 1 && vers.minor >= 26 {
+        println!("cargo:rustc-cfg=stable_i128")
+    }
+}