Revert "build: Enable custom ccache cache dir for Android"

Developers can specify ccache parameters by sourcing a personal build
environment script before envsetup. For example:

  CMHOME=$HOME/android/cm
  export USE_CCACHE=1
  export CCACHE_DIR=$CMHOME/.ccache
  $CMHOME/prebuilts/misc/linux-x86/ccache/ccache -M50G
  # Maybe someday, currently not supported in ccache 3.1.x
  # echo "max_size = 50G" > "$CCACHE_DIR/ccache.conf"

This reverts commit d99981e6.

Change-Id: Ic7b36a6d61269647aec022a86570cfa2068f65d7