[wasm] Make some libc stubs return an error instead of asserting. (#3…

…8256)

Fixes dotnet/runtime#38164.

src/mono/mono/mini/mini-wasm.c

@@ -761,24 +761,24 @@ ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count);
 
 ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count)
 {
- g_error ("sendfile");
- return 0;
+ errno = ENOTSUP;
+ return -1;
 }
 
 int
 getpwnam_r (const char *name, struct passwd *pwd, char *buffer, size_t bufsize,
  struct passwd **result)
 {
- g_error ("getpwnam_r");
- return 0;
+ *result = NULL;
+ return ENOTSUP;
 }
 
 int
 getpwuid_r (uid_t uid, struct passwd *pwd, char *buffer, size_t bufsize,
  struct passwd **result)
 {
- g_error ("getpwuid_r");
- return 0;
+ *result = NULL;
+ return ENOTSUP;
 }
 
 G_END_DECLS