The system_MKL25Z4.c file is from KL25_SC.exe, the folder:

	kl25_sc_rev10/klxx-sc-baremetal/src/cpu/headers/CMSIS/MKL25Z4/Source/Templates
	
The vectors_MKL25Z4.c file was created to conform with the assembly files 
gcc/startup_MKL25Z4.s.