For the purpose of this kind of discussion, it doesn't make any difference what the writers of Joshua really meant. We know from historical records that for at least 2000 years it was interpreted to mean that the sun revolves around the earth. We know this from the writings of people like Martin Luther.
We also know that other Biblical writings have been reinterpreted over the ages, just as Genesis will evntually be reinterpreted. Reality trumps the vanity of people who think they are the only true interpreters.
Then the weatherman who says "the sun set" must also believe in astronomy pre-Copernicus? Once again, it is merely describing how things looked from the observer's point of view. Due to that description you somehow get to what the writers of Joshua "must" have believed. Quite a leap. Reality trumps the vanity of people who think they are the only true interpreters.
Truth is absolute "And ye shall know the truth, and the truth shall make you free." John 3:18.
"Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me." John14:6