Error when make.

[MichaelChuSC]

cmake .. <---completed without error

make -j4 <- there are errors

The errors reported:
[ 2%] Built target slower_boot2
[ 5%] Built target slower_boot2_library
[ 6%] Built target pico-iie_parallel_pio_h
[ 7%] Linking CXX executable pico-iie.elf
/usr/lib/gcc/arm-none-eabi/12.2.1/../../../arm-none-eabi/bin/ld: CMakeFiles/pico-iie.dir/mcu/clock.c.o: in function clock_init': /home/scchu/pico/pico-iie/mcu/clock.c:7: undefined reference to set_sys_clock_khz'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/pico-iie.dir/build.make:1320: pico-iie.elf] Error 1
make[1]: *** [CMakeFiles/Makefile2:1788: CMakeFiles/pico-iie.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

Errors from: 1. verg_set_voltage(VREG_VOLTAGE_1_30);
2. set_sys_clock_khz(CLK_FREQUENCY_KHZ, true);

Is there somethig missed during compile??