Auto merge of #50709 - alexcrichton:revert-musl, r=sfackler

Revert #50105 until regression is fixed

Discovered at https://github.com/rust-lang/rust/pull/50105#issuecomment-388630750 it looks like this caused a regression with i686 musl, so let's revert in the meantime while a fix is worked out

src/bootstrap/builder.rs

@@ -697,10 +697,6 @@ impl<'a> Builder<'a> {
             cargo.env("RUSTC_CRT_STATIC", x.to_string());
         }
 
-        if let Some(x) = self.crt_static(compiler.host) {
-            cargo.env("RUSTC_HOST_CRT_STATIC", x.to_string());
-        }
-
         // Enable usage of unstable features
         cargo.env("RUSTC_BOOTSTRAP", "1");
         self.add_rust_test_threads(&mut cargo);