introduce minifakeroot that also works on macos

nixosModules/clanCore/zerotier/fake_root.c

@@ -0,0 +1,28 @@
+#include <stdint.h>
+typedef uint32_t uid_t;
+
+#ifdef __APPLE__
+  struct dyld_interpose {
+    const void * replacement;
+    const void * replacee;
+  };
+  #define WRAPPER(ret, name) static ret _fakeroot_wrapper_##name
+  #define WRAPPER_DEF(name) \
+    __attribute__((used)) static struct dyld_interpose _fakeroot_interpose_##name \
+      __attribute__((section("__DATA,__interpose"))) = { &_fakeroot_wrapper_##name, &name };
+#else
+  #define WRAPPER(ret, name) ret name
+  #define WRAPPER_DEF(name)
+#endif
+
+WRAPPER(uid_t, geteuid)(const char * path, int flags, ...)
+{
+    return 0; // Fake root
+}
+WRAPPER_DEF(geteuid)
+
+WRAPPER(uid_t, getuid)(const char * path, int flags, ...)
+{
+    return 0; // Fake root
+}
+WRAPPER_DEF(getuid)