We are building master branch every night for [bionic](https://kamailio.sipwise.com/job/kamailiodev-nightly-binaries/architecture=a...) with no problems.
``` /usr/bin/make -C src/ every-module make[2]: Entering directory '/tmp/buildd/kamailio-5.2.0~dev6+0~20180726010658.1165+bionic/src' CC (gcc) [M db_mysql.so] km_dbase.o CC (gcc) [M db_mysql.so] km_my_con.o CC (gcc) [M db_mysql.so] km_val.o CC (gcc) [M db_mysql.so] my_fld.o CC (gcc) [M db_mysql.so] km_row.o CC (gcc) [M db_mysql.so] my_con.o CC (gcc) [M db_mysql.so] km_res.o CC (gcc) [M db_mysql.so] my_cmd.o CC (gcc) [M db_mysql.so] db_mysql.o CC (gcc) [M db_mysql.so] my_res.o CC (gcc) [M db_mysql.so] my_uri.o CC (gcc) [M db_mysql.so] km_db_mysql.o make[4]: 'libsrdb2.so.1.0' is up to date. make[4]: 'libsrdb1.so.1.0' is up to date. LD (gcc) [M db_mysql.so] db_mysql.so make[2]: Leaving directory '/tmp/buildd/kamailio-5.2.0~dev6+0~20180726010658.1165+bionic/src' ```
And there are no related changes on db_mysql AFAICT I would say you are missing dev libraries