*: change execl sentinels from NULL to (char*)0

Signed-off-by: Rich Felker <dalias@aerifal.cx>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/libarchive/data_extract_to_command.c b/archival/libarchive/data_extract_to_command.c
index a2ce33b..5b32c2e 100644
--- a/archival/libarchive/data_extract_to_command.c
+++ b/archival/libarchive/data_extract_to_command.c
@@ -103,7 +103,7 @@
 				archive_handle->tar__to_command_shell,
 				"-c",
 				archive_handle->tar__to_command,
-				NULL);
+				(char *)0);
 			bb_perror_msg_and_die("can't execute '%s'", archive_handle->tar__to_command_shell);
 		}
 		close(p[0]);
diff --git a/archival/tar.c b/archival/tar.c
index f46f7bb..c0ceff5 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -567,7 +567,7 @@
 		xmove_fd(gzipDataPipe.rd, 0);
 		xmove_fd(tar_fd, 1);
 		/* exec gzip/bzip2 program/applet */
-		BB_EXECLP(zip_exec, zip_exec, "-f", NULL);
+		BB_EXECLP(zip_exec, zip_exec, "-f", (char *)0);
 		vfork_exec_errno = errno;
 		_exit(EXIT_FAILURE);
 	}