[beta] Do not probe for -Cembed-bitcode

This flag didn't make it to the beta branch of rustc, so remove the
probe here in Cargo. This is intended to be a very small patch to remove
the probe, since the real support is updated on master and will replace
this eventually anyway.

Author: alexcrichton

src/cargo/core/compiler/build_context/target_info.rs

@@ -105,12 +105,7 @@ impl TargetInfo {
             .args(&rustflags)
             .env_remove("RUSTC_LOG");
 
-        let mut embed_bitcode_test = process.clone();
-        embed_bitcode_test.arg("-Cembed-bitcode");
-        let supports_embed_bitcode = match kind {
-            CompileKind::Host => Some(rustc.cached_output(&embed_bitcode_test).is_ok()),
-            _ => None,
-        };
+        let supports_embed_bitcode = Some(false);
 
         if let CompileKind::Target(target) = kind {
             process.arg("--target").arg(target.rustc_target());