Add @chrisbazley's fork of clang

Author: mattgodbolt

build/build.sh

@@ -186,6 +186,11 @@ p1974-trunk)
     VERSION=p1974-trunk-$(date +%Y%m%d)
     LLVM_ENABLE_RUNTIMES+=";libunwind"
     ;;
+chrisbazley-trunk)
+    URL=https://github.com/chrisbazley/llvm-project.git
+    VERSION=chrisbazley-trunk-$(date +%Y%m%d)
+    LLVM_ENABLE_RUNTIMES+=";libunwind"
+    ;;
 rocm-*)
     if [[ "${VERSION#rocm-}" == "trunk" ]]; then
         BRANCH=amd-staging