Merge #307

307: Use build.rs for conditional compilation r=korken89 a=AfoHT

Extend the current test suite to allow for running tests on newer rustc-versions than current MSRV.

Required by #306 to add special tests for future MSRV.

To exclude an example from the regular non-nightly testing:

```
#![no_main]
#![no_std]

#[cfg(rustc_is_nightly)]
mod example {

    use panic_halt as _;

    #[rtfm::app(device = lm3s6965)]
    const APP: () = {
    <more code>
    }
}
```

Co-authored-by: Henrik Tjäder <henrik@tjaders.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/build.rs b/build.rs
index 14c3d24..fee1a6a 100644
--- a/build.rs
+++ b/build.rs
@@ -1,8 +1,13 @@
 use std::env;
+use version_check;
 
 fn main() {
     let target = env::var("TARGET").unwrap();
 
+    if version_check::Channel::read().unwrap().is_nightly() {
+        println!("cargo:rustc-cfg=rustc_is_nightly")
+    }
+
     if target.starts_with("thumbv6m") {
         println!("cargo:rustc-cfg=armv6m")
     }