Restore signal handlers in wl-copy before spawning children

We ignore SIGHUP and SIGPIPE in wl-copy itself, yet we want our child
processes, notably cat, to still get terminated if it receives SIGPIPE.
Signal handlers set to SIG_IGN unfortunately get inherited over exec, so
reset them before execing.

Fixes #190

src/types/copy-action.c

@@ -30,6 +30,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/wait.h>
+#include <signal.h>
 
 static void do_set_selection(struct copy_action *self, uint32_t serial) {
     /* Set the selection and make sure it reaches
@@ -86,6 +87,8 @@ static void do_send(struct source *source, const char *mime_type, int fd) {
             close(self->fd_to_copy_from);
             dup2(fd, STDOUT_FILENO);
             close(fd);
+            signal(SIGHUP, SIG_DFL);
+            signal(SIGPIPE, SIG_DFL);
             execlp("cat", "cat", NULL);
             perror("exec cat");
             exit(1);

src/util/files.c

@@ -33,6 +33,7 @@
 #include <stdlib.h> // exit
 #include <libgen.h> // basename
 #include <sys/wait.h>
+#include <signal.h>
 #include <syslog.h>
 
 #ifdef HAVE_MEMFD
@@ -167,6 +168,8 @@ char *infer_mime_type_from_contents(const char *file_path) {
             /* If we cannot open /dev/null, just close stdin */
             close(STDIN_FILENO);
         }
+        signal(SIGHUP, SIG_DFL);
+        signal(SIGPIPE, SIG_DFL);
         execlp("xdg-mime", "xdg-mime", "query", "filetype", file_path, NULL);
         exit(1);
     }
@@ -274,6 +277,8 @@ char *dump_stdin_into_a_temp_file() {
         }
         dup2(fd, STDOUT_FILENO);
         close(fd);
+        signal(SIGHUP, SIG_DFL);
+        signal(SIGPIPE, SIG_DFL);
         execlp("cat", "cat", NULL);
         perror("exec cat");
         exit(1);