Replace build.rs with link attributes (#205)

build.rs

@@ -1,14 +0,0 @@
-#![deny(warnings)]
-
-use std::env;
-
-fn main() {
-    let target = env::var("TARGET").expect("TARGET was not set");
-    if target.contains("windows") {
-        // for BCryptGenRandom
-        println!("cargo:rustc-link-lib=bcrypt");
-    } else if target.contains("apple-ios") {
-        // for SecRandomCopyBytes and kSecRandomDefault
-        println!("cargo:rustc-link-lib=framework=Security");
-    }
-}

src/windows.rs

@@ -11,6 +11,7 @@ use core::{ffi::c_void, num::NonZeroU32, ptr};
 
 const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
 
+#[link(name = "bcrypt")]
 extern "system" {
     fn BCryptGenRandom(
         hAlgorithm: *mut c_void,