[Minor] Fix some compiler warnings

contrib/libottery/aes_cryptobox.c

 #include "cryptobox.h"
 
 #if defined(__x86_64__) && defined(RSPAMD_HAS_TARGET_ATTR)
+#if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC push_options
 #pragma GCC target("aes")
+#endif
 #ifndef __SSE2__
 #define __SSE2__
 #endif

src/libcryptobox/base64/avx2.c

 extern const uint8_t base64_table_dec[256];
 
 #ifdef RSPAMD_HAS_TARGET_ATTR
+#if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC push_options
 #pragma GCC target("avx2")
+#endif
 #ifndef __SSE2__
 #define __SSE2__
 #endif
 	return ret;
 }
 
+#if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC pop_options
 #endif
+#endif

src/libcryptobox/base64/sse42.c

 extern const uint8_t base64_table_dec[256];
 
 #ifdef RSPAMD_HAS_TARGET_ATTR
+#if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC push_options
 #pragma GCC target("sse4.2")
+#endif
 #ifndef __SSE2__
 #define __SSE2__
 #endif
 	return ret;
 }
 
+#if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC pop_options
 #endif
+#endif

test/rspamd_dkim_test.c

 }
 #endif
 void
-rspamd_dkim_test_func ()
+rspamd_dkim_test_func (void)
 {
 #if 0
 	rspamd_dkim_context_t *ctx;

test/rspamd_dns_test.c

 }
 
 void
-rspamd_dns_test_func ()
+rspamd_dns_test_func (void)
 {
 
 	struct rspamd_config *cfg;

test/rspamd_lua_test.c

 	return 1;
 }
 
-void
+_Noreturn void
 rspamd_lua_test_func (void)
 {
 	lua_State *L = (lua_State *)rspamd_main->cfg->lua_state;

test/rspamd_mem_pool_test.c

 #define TEST2_BUF "test buffertest buffer"
 
 void
-rspamd_mem_pool_test_func ()
+rspamd_mem_pool_test_func (void)
 {
 	rspamd_mempool_t *pool;
 	rspamd_mempool_stat_t st;

test/rspamd_rrd_test.c

 const int pdp_per_cdp = 60;
 
 void
-rspamd_rrd_test_func ()
+rspamd_rrd_test_func (void)
 {
 	gchar  tmpfile[PATH_MAX];
 	struct rrd_rra_def rra[4];

test/rspamd_statfile_test.c

 #define HASHES_NUM 256
 
 void 
-rspamd_statfile_test_func ()
+rspamd_statfile_test_func (void)
 {
 	/*
 	 * XXX: broken, old, need to be rewritten

test/rspamd_url_test.c

 
 /* Function for using in glib test suite */
 void
-rspamd_url_test_func ()
+rspamd_url_test_func (void)
 {
 	/* XXX: maybe write test for this */
 }