Address review comments: remove duplicate rustc-cfg-check lines

(also put them in a better order)

Author: thejpster

cortex-m/build.rs

@@ -29,10 +29,8 @@ fn main() {
     }
 
     println!("cargo:rustc-check-cfg=cfg(armv6m)");
-    println!("cargo:rustc-check-cfg=cfg(armv7em)");
-    println!("cargo:rustc-check-cfg=cfg(armv7m)");
     println!("cargo:rustc-check-cfg=cfg(armv7m)");
-    println!("cargo:rustc-check-cfg=cfg(armv8m)");
+    println!("cargo:rustc-check-cfg=cfg(armv7em)");
     println!("cargo:rustc-check-cfg=cfg(armv8m)");
     println!("cargo:rustc-check-cfg=cfg(armv8m_base)");
     println!("cargo:rustc-check-cfg=cfg(armv8m_main)");