crt: testcases: Add a missing <exception> include for std::terminate

This is required with libc++ 23, which by default has omitted a
number of unnecessary transitive includes in headers.

Signed-off-by: Martin Storsjö <martin@martin.st>

mingw-w64-crt/testcases/t_tls_cpp.cpp

diff --git a/mingw-w64-crt/testcases/t_tls_cpp.cpp b/mingw-w64-crt/testcases/t_tls_cpp.cpp
index 59f4d5f..9007f7d 100644
--- a/mingw-w64-crt/testcases/t_tls_cpp.cpp
+++ b/mingw-w64-crt/testcases/t_tls_cpp.cpp
@@ -3,6 +3,7 @@
 
 // Standard C++ headers
 #include <iostream>
+#include <exception>
 
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>