Switch *san to clang-8 for proper backtraces

dockerfiles/xenial.docker

@@ -23,7 +23,7 @@ RUN apt-get update && \
     apt-get install -y libncurses5-dev && \
     apt-get install -y linux-headers-generic && \
     apt-get install -y graphviz && \
-    apt-get install -y clang-6.0 && \
+    apt-get install -y clang-8 && \
     apt-get install -y libhdf5-dev && \
     apt-get install -y liblua5.2-dev && \
     apt-get install -y python-sphinx && \

vars/helper.groovy

@@ -242,12 +242,12 @@ for VAR in \${JOB_VARIABLES}; do
   export \\`eval echo \\\${VAR}\\`
 done
 if [ "${buildType}" == "tsan" ]; then
-  export CC="clang-6.0"
-  export CXX="clang++-6.0"
+  export CC="clang-8"
+  export CXX="clang++-8"
   cmake /scratch/source/\${RUN_FROM_SUBDIR} -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=\${cmakeBuildType} -DSUPPRESS_AUTO_DOC_BUILD=true \${CMAKE_EXTRA_ARGS} -DCMAKE_CXX_FLAGS="-fsanitize=thread"
 elif [ "${buildType}" == "asan" ]; then
-  export CC="clang-6.0"
-  export CXX="clang++-6.0"
+  export CC="clang-8"
+  export CXX="clang++-8"
   export LSAN_OPTIONS=verbosity=1:log_threads=1
   cmake /scratch/source/\${RUN_FROM_SUBDIR} -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=\${cmakeBuildType} -DSUPPRESS_AUTO_DOC_BUILD=true \${CMAKE_EXTRA_ARGS} -DCMAKE_CXX_FLAGS="-fsanitize=address -fsanitize=undefined -fsanitize=leak"
 else