Revert "Turn on clang by default on linux."

tools/clang/scripts/update.sh

Index: tools/clang/scripts/update.sh
diff --git a/tools/clang/scripts/update.sh b/tools/clang/scripts/update.sh
index 85a33d6c51d9f531d8daf7fdf84a9e20856f8dbe..a40224c85989d5ee4698619eed58adc48202ce90 100755
--- a/tools/clang/scripts/update.sh
+++ b/tools/clang/scripts/update.sh
@@ -132,6 +132,13 @@ while [[ $# > 0 ]]; do
   shift
 done
 
+# Remove clang on bots where it was autoinstalled in r262025.
+if [[ -f "${LLVM_BUILD_DIR}/autoinstall_stamp" ]]; then
+  echo Removing autoinstalled clang and clobbering
+  rm -rf "${LLVM_BUILD_DIR}"
+  rm -rf "${THIS_DIR}/../../../out"
+fi
+
 if [[ -n "$if_needed" ]]; then
   if [[ "${OS}" == "Darwin" ]]; then
     # clang is used on Mac.
@@ -143,12 +150,6 @@ if [[ -n "$if_needed" ]]; then
     # clang previously downloaded, remove third_party/llvm-build to prevent
     # updating.
     true
-  elif [[ "${OS}" == "Linux" ]]; then
-    # Temporarily use clang on linux. Leave a stamp file behind, so that
-    # this script can remove clang again on machines where it was autoinstalled.
-    mkdir -p "${LLVM_BUILD_DIR}"
-    touch "${LLVM_BUILD_DIR}/autoinstall_stamp"
-    true
   else
     # clang wasn't needed, not doing anything.
     exit 0