When someone says "build their own chip" they do not in general mean to extract their own silicon ingots from sand, or to build their own fab. They mean to "tape out" their own SoC design and send it to a fab owner such as TSMC, Samsung, Intel for the physical manufacturing step.
Apple does not own a fab. Arm does not own a fab. Qualcomm does not own a fab. I believe IBM does not own any modern fab (some built in early 2000s, yes).