Executable isn't always run natively on Apple Silicon

[nskobelevs]

MacOS seems to like to maintain the same architecture for executables when running them. This means that if a process running on Rosetta tries to run a universal Mach-O executable, supporting both x86_64 and arm64, MacOS will also just run it via Rosetta instead of doing so natively.

In the context of doorstop - Steam's build for MacOS is currently x86_64 and runs via Rosetta meaning if the game is launched with the doorstop run script via Steam's launch options the game will be launched via Rosetta if it's shipped with a universal binary.

I've opened #79 with a proposed fix for this.

Example:
Minimal reproducible example of this behaviour, not doorstop specific but might better demonstrate what I mean.

main.c

// Compile a universal binary:
// gcc main.c -arch arm64 -arch x86_64 -o main

#include <stdio.h>

int main() {
#if defined(__aarch64__) || defined(__arm64__)
  printf("arm64\n");
#elif defined(__x86_64__)
  printf("x86_64\n");
#else
  printf("unknown\n");
#endif

  return 0;
}

When running through my native terminal we get the expected arm64 version:

❯ ./main
arm64

Similarly if we launch it indirectly via sh. (native terminal => sh gets launched natively => main gets launched natively)

❯ /bin/sh -c "exec ./main"
arm64

But if we use arch to run sh via Rosetta, the exec will also launch the executable via Rosetta:

❯ arch -x86_64 /bin/sh -c "exec ./main"
x86_64