Fix compilation warnings

[vlvkobal]

Summary

The PR fixes the following compilation warnings

sudo stop systemctl stop netdata; sudo rm -rf /var/cache/netdata/*; sudo rm -rf /var/log/netdata/*; sudo CFLAGS="-Og -ggdb -Wall -Wextra -Wformat-signedness -fno-omit-frame-pointer -fstack-protector-all -DNETDATA_INTERNAL_CHECKS=1 -D_FORTiFY_SOURCE=2 -DNETDATA_VERIFY_LOCKS=1" ./netdata-installer.sh --enable-plugin-nfacct --enable-plugin-freeipmi --disable-backend-kinesis --enable-backend-prometheus-remote-write --use-system-protobuf --disable-cloud --disable-go --disable-lto --dont-wait --dont-start-it

ml/ml-dummy.c: In function 'ml_get_host_info':
ml/ml-dummy.c:13:50: warning: control reaches end of non-void function [-Wreturn-type]
   13 | char *ml_get_host_info(RRDHOST *RH) { (void) RH; }
      |  

database/sqlite/sqlite_aclk_chart.c: In function 'queue_chart_to_aclk':
database/sqlite/sqlite_aclk_chart.c:977:33: warning: unused parameter 'st' [-Wunused-parameter]
  977 | int queue_chart_to_aclk(RRDSET *st)
      | 

database/sqlite/sqlite_aclk_alert.c:726:12: warning: 'have_recent_alarm' defined but not used [-Wunused-function]
  726 | static int have_recent_alarm(RRDHOST *host, uint32_t alarm_id, time_t mark)
      |   

and

sudo stop systemctl stop netdata; sudo rm -rf /var/cache/netdata/*; sudo rm -rf /var/log/netdata/*; sudo CFLAGS="-Og -ggdb -Wall -Wextra -Wformat-signedness -fno-omit-frame-pointer -fstack-protector-all -DNETDATA_INTERNAL_CHECKS=1 -D_FORTiFY_SOURCE=2 -DNETDATA_VERIFY_LOCKS=1" ./netdata-installer.sh --enable-plugin-nfacct --enable-plugin-freeipmi --disable-backend-kinesis --enable-backend-prometheus-remote-write --use-system-protobuf --disable-go --disable-lto --dont-wait --dont-start-it

aclk/legacy/aclk_rx_msgs.c: In function 'aclk_handle_cloud_request_v2':
aclk/legacy/aclk_rx_msgs.c:166:21: warning: 'data' may be used uninitialized in this function [-Wmaybe-uninitialized]
  166 |     cloud_req->data = data;
      |     ~~~~~~~~~~~~~~~~^~~~~~

database/sqlite/sqlite_aclk_chart.c: In function 'aclk_send_chart_event':
database/sqlite/sqlite_aclk_chart.c:411:33: warning: 'last_timestamp' may be used uninitialized in this function [-Wmaybe-uninitialized]
  411 |             wc->chart_timestamp = last_timestamp;
      |             ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

There is also a warning in SQLite

database/sqlite/sqlite3.c: In function 'pager_playback':
database/sqlite/sqlite3.c:55579:5: warning: 'memset' writing 4 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
55579 |     memset(&zSuper[-4], 0, 4);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~
database/sqlite/sqlite3.c:55561:21: note: destination object '*pPager.pTmpSpace' of size [0, 9223372036854775807]
55561 |     zSuper = &pPager->pTmpSpace[4];
      |  

but it is not fixed yet in SQLite 3.37.0.

Component Name

Anomaly detection, ACLK

Test Plan

Run Netdata build with the aforementioned options. Check if the warnings are gone except an SQLite's one.

[thiagoftsm]

I did not have warnings using gcc (GCC) 11.2.0.

[vlvkobal]

Rebased because of a merge conflict with #11841.

[thiagoftsm]

I recompiled the PR after rebase and the final result is as expected, LGTM!