anchor.diff:      echo "  cxx    = /usr/bin/clang++-3.7"  >> /root/.buckconfig && \
       echo "  cxxpp  = /usr/bin/clang++-3.7"  >> /root/.buckconfig && \
       echo "  ld     = /usr/bin/clang++-3.7"  >> /root/.buckconfig && \
  -    echo "cxxflags = -std=c++14 -O3 -g -fno-omit-frame-pointer -Wextra" >> /root/.buckconfig
  +    echo "  cxxflags = -std=c++14 ${CXXFLAGS} -Wextra" >> /root/.buckconfig
  +
   # Right now, if buckd is enabled in virtualbox one of two things will happen:
   #  - If the project is mounted on a virtualbox shared folders dir,
   #    mmap will not work, and https://github.com/facebook/buck/blob/master/src/com/facebook/buck/cxx/ObjectFileScrubbers.java
  
positive.code: 
  ARG CC=/usr/bin/gcc-5
  ARG CXX=/usr/bin/g++-5
  
  ARG FOLLY_SHA=f2a8b592861472bf47495c40519fdd778b420bc1 
  ARG WANGLE_SHA=9ed41ea931c1039d2eb80b9152577bbe714f9b71
  
negative.code: # Download and install watchman, build with g++5 tools
  RUN git clone --depth 1 --branch ${WATCHMAN_VER} https://github.com/facebook/watchman.git /usr/src/watchman && \
      cd /usr/src/watchman && \
      ldconfig && \
      ./autogen.sh && \
      ./configure && \
      make && \
  