Update the error thrown by Bazel
Hello,
The error message thrown by Bazel in step 4 should be updated.
The label of the toolchain specified in step 3 is **//toolchain:asmjs_toolchain** and not **//toolchain:asmjs_toolchain_config**.
Therefore the error message should be
```
Rule '//toolchain:asmjs_toolchain' does not exist
```
Closes
@@ -139,7 +139,7 @@ using an older release of Bazel, look for the "Configuring CROSSTOOL" tutorial.
4. Run the build again. Bazel throws the following error:
```
- Rule '//toolchain:asmjs_toolchain_config' does not exist
+ Rule '//toolchain:asmjs_toolchain' does not exist
```
Now you need to define `cc_toolchain` targets for every value in the
