On macOS this fails with:
guestunmount.c:170:5: error: call to undeclared function 'sigaction'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
170 | sigaction (SIGINT, &sa, NULL);
| ^
1 error generated.
Reported-by: Mohamed Akram
Related: https://github.com/libguestfs/libguestfs/pull/188
#include <libintl.h>
#include <poll.h>
#include <limits.h>
+#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>