Preprocess arguments to rustc to workaround cargo

rustc.sh

@@ -1,2 +1,21 @@
 #!/bin/bash
-RUST_BACKTRACE=1 rustc -L build/userspace $*
+have_o=false
+for arg in "$@"; do
+    if [[ "$arg" = "-o" ]]; then
+        have_o=true
+        break
+    fi
+done
+
+args=()
+for arg in "$@"; do
+    if [[ $have_o = true && "$arg" =~ ^extra-filename= ]]; then
+        unset args[${#args[@]}-1]
+    elif [[ $have_o = true && "$arg" =~ ^--emit= ]]; then
+        args+=("--emit=link")
+    else
+        args+=("$arg")
+    fi
+done
+
+RUST_BACKTRACE=1 exec rustc -L build/userspace "${args[@]}"