[libc] fix test build on platforms without SYS_fork

[SchrodingerZhu]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/94087.diff

1 Files Affected:

• (modified) libc/test/src/__support/threads/linux/raw_mutex_test.cpp (+4)

diff --git a/libc/test/src/__support/threads/linux/raw_mutex_test.cpp b/libc/test/src/__support/threads/linux/raw_mutex_test.cpp
index 814f6f14c87b9..aff6c8be0cb1b 100644
--- a/libc/test/src/__support/threads/linux/raw_mutex_test.cpp
+++ b/libc/test/src/__support/threads/linux/raw_mutex_test.cpp
@@ -63,7 +63,11 @@ TEST(LlvmLibcSupportThreadsRawMutexTest, PSharedLock) {
   shared->data = 0;
   LIBC_NAMESPACE::RawMutex::init(&shared->mutex);
   // Avoid pull in our own implementation of pthread_t.
+#ifdef SYS_fork
   long pid = LIBC_NAMESPACE::syscall_impl<long>(SYS_fork);
+#elif defined(SYS_clone)
+  long pid = LIBC_NAMESPACE::syscall_impl<long>(SYS_clone, SIGCHLD, 0);
+#endif
   for (int i = 0; i < 10000; ++i) {
     shared->mutex.lock(LIBC_NAMESPACE::cpp::nullopt, true);
     shared->data++;