linux-user: add gcov support to preexit_cleanup

As we don't always take the normal exit path when running a guest we
can skip the normal exit destructors where gcov normally dumps it's
info. The GCC manual suggests long running programs use __gcov_dump()
to flush out the coverage state periodically so we use that here.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

linux-user/exit.c

@@ -19,10 +19,17 @@
 #include "qemu/osdep.h"
 #include "qemu.h"
 
+#ifdef CONFIG_GCOV
+extern void __gcov_dump(void);
+#endif
+
 void preexit_cleanup(CPUArchState *env, int code)
 {
 #ifdef TARGET_GPROF
         _mcleanup();
+#endif
+#ifdef CONFIG_GCOV
+        __gcov_dump();
 #endif
         gdb_exit(env, code);
 }