crimson/os/alienstore: use homebrew counting_semaphore

std::counting_semaphore has the bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104928,
go back to our homebrew version

Signed-off-by: Xuehan Xu <[email protected]>

Author: xxhdx1985126

src/crimson/os/alienstore/thread_pool.h

@@ -15,14 +15,10 @@
 #include <seastar/core/semaphore.hh>
 #include <seastar/core/sharded.hh>
 
-#if __cplusplus > 201703L
-#include <semaphore>
-namespace crimson {
-  using std::counting_semaphore;
-}
-#else
+// std::counting_semaphore is buggy in libstdc++-11
+// (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104928),
+// so we switch back to the homebrew version for now.
 #include "semaphore.h"
-#endif
 
 namespace crimson::os {