Only try to create .compose-cache directory and do not delete it on ever...

...y start of X.

The old deletion method did not work and produced the following error messages

    rm: cannot remove ‘/home/pascal/.compose-cache’: Is a directory
    mkdir: cannot create directory ‘/home/pascal/.compose-cache’: File exists

I cannot see old files accumulate, so just creating the directory and let X
do the garbage collection should work fine.