system path filtering needs to normalize paths first

x86_64-pc-linux-gnu-g++ -Wl,-O1 -Wl,--as-needed -Wl,--no-undefined -shared -o libqsqlmysql.so .obj/main.o .obj/qsql_mysql.o .obj/moc_qsql_mysql_p.o  -L/usr/lib64/mysql -Wl,-O1 -Wl,--as-needed -m64 -rdynamic -lmysqlclient_r -L/usr//lib64 -lz -lcrypt -lnsl -lm -L/usr/lib64/ -lssl -lcrypto -L/var/tmp/portage/dev-qt/qtsql-5.3.0_rc/work/qtbase-opensource-src-5.3.0-RC/lib -lQt5Sql -lQt5Core -lpthread  
.obj/qsql_mysql.o: In function `QMYSQLDriver::QMYSQLDriver(QObject*)':
qsql_mysql.cpp:(.text+0x34c1): undefined reference to `QSqlError::QSqlError(QString const&, QString const&, QSqlError::ErrorType, QString const&)'

$ mysql_config --libs_r
-Wl,--hash-style=gnu -Wl,-O1 -Wl,--as-needed -rdynamic -L/usr/lib64/mysql -lmysqlclient_r -L/usr//lib64 -lz -lpthread -lcrypt -lnsl -lm -lpthread -L/usr/lib64/ -lssl -lcrypto