build: Remove getrandom_uwp cfg

As our minimum rust version is 1.33, we can just use `target_vendor`.

Author: josephlr

build.rs

@@ -7,8 +7,6 @@ fn main() {
     if target.contains("-uwp-windows-") {
         // for BCryptGenRandom
         println!("cargo:rustc-link-lib=bcrypt");
-        // to work around unavailability of `target_vendor` on Rust 1.33
-        println!("cargo:rustc-cfg=getrandom_uwp");
     } else if target.contains("windows") {
         // for RtlGenRandom (aka SystemFunction036)
         println!("cargo:rustc-link-lib=advapi32");

src/lib.rs

@@ -177,7 +177,7 @@ cfg_if! {
     } else if #[cfg(target_os = "vxworks")] {
         mod util_libc;
         #[path = "vxworks.rs"] mod imp;
-    } else if #[cfg(all(windows, getrandom_uwp))] {
+    } else if #[cfg(all(windows, target_vendor = "uwp"))] {
         #[path = "windows_uwp.rs"] mod imp;
     } else if #[cfg(windows)] {
         #[path = "windows.rs"] mod imp;