travis: Install clang-11 for ASAN/UBSAN job

[skip appveyor]

.travis.yml

@@ -99,12 +99,21 @@ jobs:
     - stage: baseline
       name: clang-asan
       os: linux
-      compiler: clang
+      compiler: clang-11
       # Use Lua so that ASAN can test our embedded Lua support. 8fec4d53d0f6
       env:
         - CLANG_SANITIZER=ASAN_UBSAN
         - CMAKE_FLAGS="$CMAKE_FLAGS -DPREFER_LUA=ON"
+        - SYMBOLIZER=asan_symbolize-11
         - *common-job-env
+      addons:
+        apt:
+          sources:
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - *common-apt-packages
+            - clang-11
     - name: gcc-coverage (gcc 9)
       os: linux
       compiler: gcc-9

ci/common/test.sh

@@ -82,7 +82,7 @@ valgrind_check() {
 
 check_sanitizer() {
   if test -n "${CLANG_SANITIZER}"; then
-    check_logs "${1}" "*san.*"
+    check_logs "${1}" "*san.*" | ${SYMBOLIZER:-cat}
   fi
 }