cgi-io: fix stray semicolon

Remove an improperly placed semicolon in order to solve the following
compiler error:

.../main.c:144:3: error: this 'if' clause does not guard... [-Werror=misleading-indentation]
    if (execl("/bin/busybox", "/bin/busybox", "md5sum", file, NULL));
    ^~
    .../main.c:145:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
    return NULL;
    ^~~~~~
    cc1: all warnings being treated as errors

Fixes #4723.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

net/cgi-io/Makefile

@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=cgi-io
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_LICENSE:=GPL-2.0+
 

net/cgi-io/src/main.c

@@ -141,7 +141,7 @@ md5sum(const char *file)
 		close(fds[0]);
 		close(fds[1]);
 
-		if (execl("/bin/busybox", "/bin/busybox", "md5sum", file, NULL));
+		if (execl("/bin/busybox", "/bin/busybox", "md5sum", file, NULL))
 			return NULL;
 
 		break;