[TSan][libdispatch] Replace usage of NSMutableData with stack array

test/tsan/Darwin/gcd-fd.mm

int main(int argc, const char *argv[]) {
   dispatch_semaphore_t sem = dispatch_semaphore_create(0);
 
   NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"temp-gcd-io.%d", getpid()]];
 
   dispatch_io_t channel = dispatch_io_create_with_path(DISPATCH_IO_STREAM, path.fileSystemRepresentation, O_CREAT | O_WRONLY,
       0666, queue, ^(int error) { });
   dispatch_io_set_high_water(channel, 1);
 
-  NSData *ns_data = [NSMutableData dataWithLength:1000];
-  dispatch_data_t data = dispatch_data_create(ns_data.bytes, ns_data.length, NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  char buf[1000];
+  dispatch_data_t data = dispatch_data_create(buf, sizeof(buf), NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
 
   my_global++;
   dispatch_io_write(channel, 0, data, queue, ^(bool done, dispatch_data_t remainingData, int error) {
     my_global++;
     dispatch_async(queue, ^{
       my_global++;
       if (done) {
         dispatch_semaphore_signal(sem);

test/tsan/Darwin/gcd-io-barrier-race.mm

int main(int argc, const char *argv[]) {
   fprintf(stderr, "Hello world.\n");
   print_address("addr=", 1, &my_global);
   barrier_init(&barrier, 2);
 
   queue = dispatch_queue_create("my.queue", DISPATCH_QUEUE_CONCURRENT);
   sem = dispatch_semaphore_create(0);
   NSString *ns_path = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"temp-gcd-io.%d", getpid()]];
   path = ns_path.fileSystemRepresentation;
-  NSData *ns_data = [NSMutableData dataWithLength:1000];
-  data = dispatch_data_create(ns_data.bytes, ns_data.length, NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  char buf[1000];
+  data = dispatch_data_create(buf, sizeof(buf), NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
   
   dispatch_io_t channel = dispatch_io_create_with_path(DISPATCH_IO_STREAM, path, O_CREAT | O_WRONLY, 0666, queue, ^(int error) { });
   if (! channel) abort();
   dispatch_io_set_high_water(channel, 1);
 
   dispatch_io_write(channel, 0, data, queue, ^(bool done, dispatch_data_t remainingData, int error) {
     if (error) abort();
     my_global = 42;

test/tsan/Darwin/gcd-io-barrier.mm

 
 int main(int argc, const char *argv[]) {
   fprintf(stderr, "Hello world.\n");
   
   queue = dispatch_queue_create("my.queue", DISPATCH_QUEUE_CONCURRENT);
   sem = dispatch_semaphore_create(0);
   NSString *ns_path = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"temp-gcd-io.%d", getpid()]];
   path = ns_path.fileSystemRepresentation;
-  NSData *ns_data = [NSMutableData dataWithLength:1000];
-  data = dispatch_data_create(ns_data.bytes, ns_data.length, NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  char buf[1000];
+  data = dispatch_data_create(buf, sizeof(buf), NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
   
   dispatch_io_t channel = dispatch_io_create_with_path(DISPATCH_IO_STREAM, path, O_CREAT | O_WRONLY, 0666, queue, ^(int error) { });
   if (! channel) abort();
   dispatch_io_set_high_water(channel, 1);
 
   for (int i = 0; i < 1000; i++) {
     dispatch_io_barrier(channel, ^{
       my_global = 42;

test/tsan/Darwin/gcd-io-race.mm

int main(int argc, const char *argv[]) {
   fprintf(stderr, "Hello world.\n");
   print_address("addr=", 1, &my_global);
   barrier_init(&barrier, 2);
   
   queue = dispatch_queue_create("my.queue", DISPATCH_QUEUE_CONCURRENT);
   sem = dispatch_semaphore_create(0);
   NSString *ns_path = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"temp-gcd-io.%d", getpid()]];
   path = ns_path.fileSystemRepresentation;
-  NSData *ns_data = [NSMutableData dataWithLength:1000];
-  data = dispatch_data_create(ns_data.bytes, ns_data.length, NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  char buf[1000];
+  data = dispatch_data_create(buf, sizeof(buf), NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
   
   dispatch_io_t channel = dispatch_io_create_with_path(DISPATCH_IO_STREAM, path, O_CREAT | O_WRONLY, 0666, queue, ^(int error) { });
   if (! channel) abort();
   dispatch_io_set_high_water(channel, 1);
   
   dispatch_io_write(channel, 0, data, queue, ^(bool done, dispatch_data_t remainingData, int error) {
     my_global = 42;
     barrier_wait(&barrier);

test/tsan/Darwin/gcd-io.mm

 
 int main(int argc, const char *argv[]) {
   fprintf(stderr, "Hello world.\n");
   
   queue = dispatch_queue_create("my.queue", DISPATCH_QUEUE_SERIAL);
   sem = dispatch_semaphore_create(0);
   NSString *ns_path = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"temp-gcd-io.%d", getpid()]];
   path = ns_path.fileSystemRepresentation;
-  NSData *ns_data = [NSMutableData dataWithLength:1000];
-  data = dispatch_data_create(ns_data.bytes, ns_data.length, NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  char buf[1000];
+  data = dispatch_data_create(buf, sizeof(buf), NULL, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
   
   test_dispatch_io_write();
   test_dispatch_write();
   test_dispatch_io_read();
   test_dispatch_read();
   
   fprintf(stderr, "Done.\n");
   return 0;
 }
 
 // CHECK: Hello world.
 // CHECK-NOT: WARNING: ThreadSanitizer
 // CHECK: Done.