botan: let the build script detect the platform and compiler (#72811)
botan: let the build script detect the platform and compiler (#72811)

Checked locally:
INFO: Implicit --cc-bin=clang++ due to environment variable CXX
INFO: Autodetected platform information: OS="Darwin" machine="x86_64" proc="i386"
INFO: Guessing target OS is darwin (use --os to set)
INFO: Guessing target processor is a x86_64 (use --cpu to set)

Fixes the build on Linux
Homebrew/homebrew-core,filcab/homebrew-core,stgraber/homebrew-core,adam-moss/homebrew-core,stgraber/homebrew-core,chrisfinazzo/homebrew-core,sjackman/homebrew-core,zyedidia/homebrew-core,adam-moss/homebrew-core,uyjulian/homebrew-core,JCount/homebrew-core,nbari/homebrew-core,mbcoguno/homebrew-core,mbcoguno/homebrew-core,lemzwerg/homebrew-core,Moisan/homebrew-core,nbari/homebrew-core,mbcoguno/homebrew-core,cblecker/homebrew-core,makigumo/homebrew-core,JCount/homebrew-core,filcab/homebrew-core,cblecker/homebrew-core,mfikes/homebrew-core,Moisan/homebrew-core,mfikes/homebrew-core,lemzwerg/homebrew-core,sjackman/homebrew-core,Linuxbrew/homebrew-core,zyedidia/homebrew-core,nandub/homebrew-core,nandub/homebrew-core,uyjulian/homebrew-core,makigumo/homebrew-core,Homebrew/homebrew-core,chrisfinazzo/homebrew-core,Linuxbrew/homebrew-core