"Error: Unsupported value for --arch" when building on Fedora

[nicholas-rh]

On Fedora 38, attempting to build the project results in the following error:

ispc -O2 --arch= --target= --opt=fast-math --pic -o ispc_texcomp/kernel_astc_ispc.o -h ispc_texcomp/kernel_astc_ispc.h ispc_texcomp/kernel_astc.ispc
Error: Unsupported value for --arch, supported values are: x86, x86-64, arm, aarch64 
make: *** [Makefile.linux:53: ispc_texcomp/kernel_astc_ispc.o] Error 255

This seems to be caused by the invocation of uname -p which outputs in "unknown" on my x64 machine. Running uname -m outputs "x86_64" as expected, and modifying the makefile to use this flag instead allows for the build to succeed. Both flags seem to work on Ubuntu 22.04 LTS. According to the man pages the -p flag is "non-portable."