libstdc++-v3: std_thread: include shared_ptr.h

shared_ptr was being used inside of a _GLIBCXX_THREAD_ABI_COMPAT
block. Include the header which defines that class.

Signed-off-by: Christopher Friedt <chris@friedt.co>

Author: cfriedt-friedtco

libstdc++-v3/include/bits/std_thread.h

@@ -41,6 +41,7 @@
 #include <bits/invoke.h>	// std::__invoke
 #include <bits/refwrap.h>       // not required, but helpful to users
 #include <bits/unique_ptr.h>	// std::unique_ptr
+#include <bits/shared_ptr.h>	// std::shared_ptr
 
 #ifdef _GLIBCXX_HAS_GTHREADS
 # include <bits/gthr.h>