Fix test_unistd_isatty to open /dev/stdout in write only mode. NFC (#26544)

Author: sbc100

test/test_other.py

@@ -13165,13 +13165,17 @@ def test_unistd_swab(self):
     self.do_run_in_out_file_test('unistd/swab.c')
 
   @also_with_noderawfs
+  @crossplatform
+  @no_deno('https://github.com/denoland/deno/issues/32995')
   def test_unistd_isatty(self):
     if '-DNODERAWFS' in self.cflags:
       # Under NODERAWFS istty reports accurate information about the file descriptors
       # of the node process. When we run tests we always capture stdout so we never expect
       # stdout to be a tty.
       stdin_isatty = os.isatty(0)
       self.cflags += ['-DEXPECT_STDOUT=0', f'-DEXPECT_STDIN={int(stdin_isatty)}']
+      if WINDOWS:
+        self.skipTest('depends on /dev filesystem')
     self.do_runf('unistd/isatty.c', 'success')
 
   def test_unistd_login(self):
@@ -13184,7 +13188,7 @@ def test_unistd_sleep(self):
   @with_all_fs
   def test_unistd_fstatfs(self):
     if '-DNODERAWFS' in self.cflags and WINDOWS:
-      self.skipTest('Cannot look up /dev/stdout on windows')
+      self.skipTest('depends on /dev filesystem')
     self.do_run_in_out_file_test('unistd/fstatfs.c', cflags=['-sASSERTIONS=2'])
 
   @no_windows("test is Linux-specific")

test/unistd/isatty.c

@@ -25,6 +25,8 @@ int main() {
   printf("EXPECT_STDIN: %d\n", EXPECT_STDIN);
   printf("EXPECT_STDOUT: %d\n", EXPECT_STDOUT);
 
+  printf("stdin -> %d\n", isatty(0));
+  printf("stdout -> %d\n", isatty(1));
   assert(isatty(0) == EXPECT_STDIN);
   assert(isatty(1) == EXPECT_STDOUT);
 
@@ -35,18 +37,22 @@ int main() {
 
   fd = open("/dev/stdin", O_RDONLY);
   assert(fd >= 0);
+  printf("/dev/stdin -> %d\n", isatty(fd));
   assert(isatty(fd) == EXPECT_STDIN);
 
-  fd = open("/dev/stdout", O_RDONLY);
+  fd = open("/dev/stdout", O_WRONLY);
   assert(fd >= 0);
+  printf("/dev/stdout -> %d\n", isatty(fd));
   assert(isatty(fd) == EXPECT_STDOUT);
 
   fd = open("/dev/null", O_RDONLY);
   assert(fd >= 0);
+  printf("/dev/null -> %d\n", isatty(fd));
   assert(isatty(fd) == 0);
 
   fd = open("/dev", O_RDONLY);
   assert(fd >= 0);
+  printf("/dev -> %d\n", isatty(fd));
   assert(isatty(fd) == 0);
 
   puts("success");