Generate seperate release names for LLVM and GCC toolchain release artifacts

Author: patrick-rivos

.github/workflows/nightly-release.yaml

@@ -101,7 +101,7 @@ jobs:
             *)
               MODE="elf";;
           esac
-          echo ::set-output name=TOOLCHAIN_NAME::riscv$BITS-$MODE-${{ matrix.os }}-nightly
+          echo ::set-output name=TOOLCHAIN_NAME::riscv$BITS-$MODE-${{ matrix.os }}-${{ matrix.compiler }}-nightly
 
       - uses: actions/upload-artifact@v2
         with: