[Bazel] fix llvm bin path (#888)

bazel/emscripten_toolchain/link_wrapper.py

diff --git a/bazel/emscripten_toolchain/link_wrapper.py b/bazel/emscripten_toolchain/link_wrapper.py
index 2f156d8..ce10dae 100644
--- a/bazel/emscripten_toolchain/link_wrapper.py
+++ b/bazel/emscripten_toolchain/link_wrapper.py
@@ -105,7 +105,7 @@
   # is the blaze output path; we want it to be just the filename.
 
   llvm_objcopy = os.path.join(
-      os.environ['EMSCRIPTEN'], 'llvm-bin/llvm-objcopy')
+      os.environ['EM_BIN_PATH'], 'bin/llvm-objcopy')
   # First, check to make sure the .wasm file has the header that needs to be
   # rewritten.
   rtn = subprocess.call([