In some environments, signal.h is already included, but not in others which cause compilation to fail, so explictly include it. Closes #11478
@@ -178,6 +178,7 @@ struct Curl_addrinfo *Curl_ipv4_resolve_r(const char *hostname,
#endif /* CURLRES_AMIGA */
#ifdef USE_AMISSL
+#include <signal.h>
int Curl_amiga_select(int nfds, fd_set *readfds, fd_set *writefds,
fd_set *errorfds, struct timeval *timeout)
{