meson build system

• Closes #350 (closed) (build system)
• Closes #212 (closed) (static build)
• Closes #279 (closed) (module namespace)
• Closes #290 (closed) (remove go modules support)
• Closes #338 (closed) (same vars for make / make install)
• Closes #451 (closed) (shadow lua global by func param)

Remaining TODOs

• fix CI tests
• update scripts for OBS to build successfully
• make sure OSX build works
• create migration documentation
• document/resolve missing parts (coverage)
• update respdiff toolchain
• document modules' lua dependencies

Review

• tarball includes the same files (see https://gitlab.labs.nic.cz/knot/knot-resolver/merge_requests/771#note_99606)
• CFLAGS, LDFLAGS for dev build hasn't changed unintentionally
• git diff doesn't contain forgotten TODO
• no commit contains DROP, WIP or TODO in title/message
• the same test suite is executed in CI
• check every module loads when installed (incl. dnstap)
• distro packages
  • no files were unintentionally removed
    • arch
    • deb
    • rpm
  • builds in OBS pass package test on a clean system
  • installed files/dir didn't unintentionally change permissions / owner
    • arch
    • deb
    • rpm
  • debian/ubuntu systemd works as before (service restart during update etc.)

Pre-merge

• [respdiff] - merge respdiff!50 (merged), update test infrastructure

daemon/network.c

@@ -250,7 +250,7 @@ int network_listen_fd(struct network *net, int fd, bool use_tls)
 	/* Extract local address and socket type. */
 	int sock_type = SOCK_DGRAM;
 	socklen_t len = sizeof(sock_type);
-	int ret = getsockopt(fd, SOL_SOCKET, SO_TYPE, &sock_type, &len);	
+	int ret = getsockopt(fd, SOL_SOCKET, SO_TYPE, &sock_type, &len);
 	if (ret != 0) {
 		return kr_error(EBADF);
 	}
@@ -364,9 +364,9 @@ void network_new_hostname(struct network *net, struct engine *engine)
 	}
 }
 
+#ifdef SO_ATTACH_BPF
 static int set_bpf_cb(const char *key, void *val, void *ext)
 {
-#ifdef SO_ATTACH_BPF
 	endpoint_array_t *endpoints = (endpoint_array_t *)val;
 	assert(endpoints != NULL);
 	int *bpffd = (int *)ext;
@@ -383,13 +383,9 @@ static int set_bpf_cb(const char *key, void *val, void *ext)
 			return 1; /* return error (and stop iterating over net->endpoints) */
 		}
 	}
-#else
-	kr_log_error("[network] SO_ATTACH_BPF socket option doesn't supported\n");
-	(void)key; (void)val; (void)ext;
-	return 1;
-#endif
 	return 0; /* OK */
 }
+#endif
 
 int network_set_bpf(struct network *net, int bpf_fd)
 {
@@ -408,9 +404,9 @@ int network_set_bpf(struct network *net, int bpf_fd)
 	return 1;
 }
 
+#ifdef SO_DETACH_BPF
 static int clear_bpf_cb(const char *key, void *val, void *ext)
 {
-#ifdef SO_DETACH_BPF
 	endpoint_array_t *endpoints = (endpoint_array_t *)val;
 	assert(endpoints != NULL);
 
@@ -427,13 +423,9 @@ static int clear_bpf_cb(const char *key, void *val, void *ext)
 		/* Proceed even if setsockopt() failed,
 		 * as we want to process all opened sockets. */
 	}
-#else
-	kr_log_error("[network] SO_DETACH_BPF socket option doesn't supported\n");
-	(void)key; (void)val; (void)ext;
-	return 1;
-#endif
 	return 0;
 }
+#endif
 
 void network_clear_bpf(struct network *net)
 {