Fixes compilation with musl
Patch by Natanael Copa
https://gitlab.alpinelinux.org/alpine/aports/-/issues/2890
https://bugs.gentoo.org/717202

--- a/dnstop.c
+++ b/dnstop.c
@@ -69,7 +69,7 @@
 #define ETHERTYPE_IPV6 0x86DD
 #endif
 
-#if defined(__linux__) || defined(__GLIBC__) || defined(__GNU__)
+#if defined(__GLIBC__) || defined(__GNU__)
 #define uh_dport dest
 #define uh_sport source
 #endif