Clang is built as a multi-target compiler, so aarch64-linux-android21-clang and corresponding clang and clang++ files for different Android ABI versions (replacing 21 with numbers in the range 22 to 35 or so) are small scripts that invoke the bare clang and clang++ executables with appropriate target and ABI options.

 https://stackoverflow.com/questions/79660791/ndk-toolchain-aarch64-linux-android-folder-not-found