Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. mingw-libjpeg-turbo appears to use an earlier version of autoconf, preventing its being built. This can be fixed in of three ways (In order of preference): 1. Work with upstream to migrate the package to autoconf 2.69. 2. Rerun autoconf or autoreconf in %prep or %build prior to running configure. 3. Apply the patch at http://ausil.fedorapeople.org/aarch64/mingw-libjpeg-turbo/mingw-libjpeg-turbo-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
Looks like a false positive. We use cmake for building mingw-libjpeg-turbo; not autotools.