Disable fuzztest subprocess library on Apple tvOS

On tvOS, creating child processes is forbidden at an API level, so the
posix_spawn_* functions used by FuzzTest in the subprocess code cause
build errors.

This change disables the subprocess library on Apple tvOS to avoid
calling unsupported functions.

This isssue is similar to b222049

Co-Authored-By: kubo@igalia.com

fuzztest/internal/subprocess.cc

diff --git a/fuzztest/internal/subprocess.cc b/fuzztest/internal/subprocess.cc
index a670bd7..fe7fb1e 100644
--- a/fuzztest/internal/subprocess.cc
+++ b/fuzztest/internal/subprocess.cc
@@ -34,6 +34,10 @@
 #include <utility>
 #include <vector>
 
+#if defined(__APPLE__)
+#include <TargetConditionals.h>
+#endif
+
 #include "absl/container/flat_hash_map.h"
 #include "absl/functional/function_ref.h"
 #include "absl/strings/str_cat.h"
@@ -49,8 +53,10 @@
 
 namespace fuzztest::internal {
 
-#if !defined(_MSC_VER) && !(defined(__ANDROID_MIN_SDK_VERSION__) && \
-                            __ANDROID_MIN_SDK_VERSION__ < 28)
+#if !defined(_MSC_VER) &&                     \
+    !(defined(__ANDROID_MIN_SDK_VERSION__) && \
+      __ANDROID_MIN_SDK_VERSION__ < 28) &&    \
+    !(defined(TARGET_OS_TV) && TARGET_OS_TV)
 
 TerminationStatus::TerminationStatus(int status) : status_(status) {}
 
@@ -335,6 +341,9 @@
   FUZZTEST_INTERNAL_CHECK(
       false,
       "Subprocess library not implemented on older Android NDK versions yet");
+#elif defined(TARGET_OS_TV) && TARGET_OS_TV
+  FUZZTEST_INTERNAL_CHECK(
+      false, "Subprocess library not implemented on Apple tvOS yet");
 #else
   SubProcess proc;
   return proc.Run(command_line, on_stdout_output, on_stderr_output, environment,