[CI] add assert-enabled MLIR option (#78)

This deprecates the use of release-build LLVM hosted by the LLVM project, which makes debugging harder for developers.

This PR implements the following solution:
1. Create LLVM release tarballs with assert enabled on our own (using Docker)
2. Host them in our own GitHub repositories
3. Use our LLVM for CI and/or development if `TRITON_USE_ASSERT_ENABLED_LLVM=1` is set.

.github/workflows/integration-tests.yml

@@ -47,7 +47,7 @@ jobs:
         run: |
           alias python='python3'
           cd python
-          pip3 install -e '.[tests]'
+          TRITON_USE_ASSERT_ENABLED_LLVM=TRUE pip3 install -e '.[tests]'
 
       - name: Run lit tests
         run: |