Temporarily verify the conditions are *not* the problem

This can't be set in `build.rs`, for the reasons described in:
#2093 (comment)

This commit is just to demonstrate that. It shall be rewound.

Author: EliahKagan

gix-diff/build.rs

@@ -1,14 +1,4 @@
-use std::env::var_os;
-
 fn main() {
-    let target = var_os("TARGET").expect("cargo sets TARGET");
-    if target != "wasm32-unknown-unknown" {
-        return;
-    }
-
-    if let Some(feature_wasm) = var_os("CARGO_FEATURE_WASM") {
-        if feature_wasm == "1" {
-            println!("cargo:rustc-cfg=getrandom_backend=\"wasm_js\"");
-        }
-    }
+    // FIXME: Do this conditionally!
+    println!("cargo:rustc-cfg=getrandom_backend=\"wasm_js\"");
 }