Added feature `no_unwind_protection` for tests. build.rs: Added `rustc-check-cfg` for cfg flag `nightly`.

Fortune for stackalloc's current commit: Half curse − 半凶

Cargo.toml

@@ -19,3 +19,6 @@ rustc_version = "0.2"
 [features]
 default = []
 no_std = []
+
+# for tests
+no_unwind_protection = []

build.rs

@@ -25,6 +25,7 @@ fn build_tramp()
 fn main() {
     // Assert we haven't travelled back in time
     assert!(version().unwrap().major >= 1);
+    println!("cargo::rustc-check-cfg=cfg(nightly)");
 
     // Set cfg flags depending on release channel
     match version_meta().unwrap().channel {