rust-lld-wrapper: Remove export-table to prevent conflict

Without this patch, the following error is thrown:
  rust-lld: error: --import-table and --export-table may not be used together

Tested on the following nightly versions:

rustc 1.30.0-nightly (7e8ca9f8b 2018-08-03)
rustc 1.30.0-nightly (33b923fd4 2018-08-18)

tools/rust-lld-wrapper

@@ -12,6 +12,7 @@ def main():
 
     # filter out args inserted by rustc
     TO_REMOVE = {
+        "--export-table",
         "--stack-first",
         "--strip-debug", # TODO: Make this configurable
     }