mask all signals in libhackrf transfer_threadproc (#1330)

* mask all signals in libhackrf transfer_threadproc

hackrf_transfer uses pause() and SIGALRM to print statistics and POSIX doesn't
specify which thread must recieve the signal, block all signals here, so we
don't interrupt their reception by hackrf_transfer or any other app which uses
the library (#1323)

* fix windows build and remove empty line

host/libhackrf/src/hackrf.c

@@ -27,6 +27,7 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSI
 #include <string.h>
 #ifndef _WIN32
 	#include <unistd.h>
+	#include <signal.h>
 #endif
 #include <libusb.h>
 
@@ -1763,6 +1764,20 @@ static void* transfer_threadproc(void* arg)
 	int error;
 	struct timeval timeout = {0, 500000};
 
+	/*
+	 * hackrf_transfer uses pause() and SIGALRM to print statistics and
+	 * POSIX doesn't specify which thread must recieve the signal, block all
+	 * signals here, so we don't interrupt their reception by
+	 * hackrf_transfer or any other app which uses the library (#1323)
+	 */
+#ifndef _WIN32
+	sigset_t signal_mask;
+	sigfillset(&signal_mask);
+	if (pthread_sigmask(SIG_BLOCK, &signal_mask, NULL) != 0) {
+		return NULL;
+	}
+#endif
+
 	while (device->do_exit == false) {
 		error = libusb_handle_events_timeout(g_libusb_context, &timeout);
 		if ((error != 0) && (error != LIBUSB_ERROR_INTERRUPTED)) {