typeset -U path

pathdirs=(
  ~/arm-coding/gcc-arm-none-eabi-4_8-2014q1/bin \
  ~/arm-coding/git/lm4tools/lm4flash \
  ~/arm-coding/openocd-bin
)

for dir in $pathdirs; do
  if [ -d $dir ]; then
    path+=$dir
  fi
done