message: run only the MicroBenchmarks and SingleSource dirs
  only compile C code with alive2, for C++ just use clang++
  this configuration takes about 15 minutes on my group's big 128-thread machine
diff: @@ -15,7 +15,7 @@ fi
  WORK=$1
  ALIVECC=@CMAKE_BINARY_DIR@/alivecc
  -ALIVEPP=@CMAKE_BINARY_DIR@/alive++
  +ALIVEPP=@LLVM_BINARY_DIR@/bin/clang++
  export ALIVECC_OVERWRITE_REPORTS=1
  export ALIVECC_SUBPROCESS_TIMEOUT=600
  @@ -29,10 +29,12 @@ git clone https://github.com/llvm/llvm-test-suite.git test-suite
  mkdir test-suite-build
  cd test-suite-build
  -cmake -DCMAKE_C_COMPILER=$ALIVECC -DCMAKE_CXX_COMPILER=$ALIVEPP -C../test-suite/cmake/caches/O3.cmake ../test-suite -DTEST_SUITE_SUBDIRS=SingleSource
  +cmake -DCMAKE_C_COMPILER=$ALIVECC -DCMAKE_CXX_COMPILER=$ALIVEPP -C../test-suite/cmake/caches/O3.cmake ../test-suite -DTEST_SUITE_SUBDIRS="MicroBenchmarks;SingleSource"
  -# 8 GB
  -ulimit -m 8388608 -v 8388608
  +# 7 GB
  +ulimit -m 7000000 -v 7000000
  # intentionally limit make-level parallelism to < number of cores
  time make -j16
  +
  +echo Normal termination.
  