Revert "add clad (a clang plugin) (#80)"

This reverts commit d792c84.

See compiler-explorer/compiler-explorer#7109 - we can't get
this to build currently and I think we should consider it being separate from the
compiler (even if it needs the compiler source to build)

build/build.sh

@@ -17,9 +17,6 @@ NINJA_TARGET=install
 NINJA_TARGET_RUNTIMES=install-runtimes
 TAG=
 declare -a PATCHES_TO_APPLY
-EXTERNAL_PROJECT_DIR=${ROOT}/external
-declare -a EXTERNAL_PROJECT_URLS
-declare -a LLVM_EXTERNAL_PROJECTS_LIST
 
 case $VERSION in
 ce-trunk)
@@ -337,12 +334,6 @@ mlir-*)
         if [[ $MAJOR -ge 18 ]]; then
             CMAKE_EXTRA_ARGS+=("-DLIBCXX_INSTALL_MODULES=ON")
         fi
-
-        if [[ $MAJOR -eq 18 ]]; then
-            EXTERNAL_PROJECT_URLS+=("https://github.com/vgvassilev/clad.git")
-            LLVM_EXTERNAL_PROJECTS_LIST+=("clad")
-            CMAKE_EXTRA_ARGS+=("-DLLVM_EXTERNAL_CLAD_SOURCE_DIR=${EXTERNAL_PROJECT_DIR}/clad")
-        fi
         ;;
     esac
     ;;
@@ -392,16 +383,6 @@ for PATCH_TO_APPLY in "${PATCHES_TO_APPLY[@]}"; do
     git -C "${ROOT}/llvm-project" apply "${PATCH_TO_APPLY}" -v
 done
 
-# Setup external projects
-mkdir -p "${EXTERNAL_PROJECT_DIR}"
-for LLVM_EXTERNAL_PROJECT in "${!EXTERNAL_PROJECT_URLS[@]}"; do
-    git clone --depth 1 "${EXTERNAL_PROJECT_URLS[LLVM_EXTERNAL_PROJECT]}" "${EXTERNAL_PROJECT_DIR}/${LLVM_EXTERNAL_PROJECTS_LIST[LLVM_EXTERNAL_PROJECT]}"
-done
-LLVM_EXTERNAL_PROJECTS=
-for LLVM_EXTERNAL_PROJECT in "${LLVM_EXTERNAL_PROJECTS_LIST}"; do
-    LLVM_EXTERNAL_PROJECTS+="${LLVM_EXTERNAL_PROJECT};";
-done
-
 # For older LLVM versions, merge runtime and projects
 # August 2021 is when bootstrapping become necessary, bootstrapping might have been supported previously a few years prior
 COMMIT_DATE=$(cd "${ROOT}/llvm-project/llvm" && git show -s --format=%ct HEAD)
@@ -432,7 +413,6 @@ cmake \
     -G "Ninja" "${ROOT}/llvm-project/llvm" \
     -DLLVM_ENABLE_PROJECTS="${LLVM_ENABLE_PROJECTS}" \
     -DLLVM_ENABLE_RUNTIMES="${LLVM_ENABLE_RUNTIMES}" \
-    -DLLVM_EXTERNAL_PROJECTS="${LLVM_EXTERNAL_PROJECTS}" \
     -DCMAKE_BUILD_TYPE:STRING=Release \
     -DCMAKE_INSTALL_PREFIX:PATH="${STAGING_DIR}" \
     -DCMAKE_C_COMPILER:PATH="/opt/compiler-explorer/gcc-${GCC_VERSION}/bin/gcc" \