chkpriv: respect $sysconfdir for config files directory #425

Job	Run time
code formatting check	16s
cppcheck	18m 59s
min features with gcc	2m 39s
min features with g++	2m 38s
min features with clang	2m 11s
max features with gcc	4m 1s
max features with g++	2m 28s
max features with clang	4m 16s
max features with clang and AddressSanitized	3m 4s
max features with gcc and DEBUG	2m 34s
max features with gcc for 32-bit arch (legacy OS)	1m 37s
max features with g++ for 32-bit arch (legacy OS)	1m 52s
max features with clang for 32-bit arch (legacy OS)	2m 28s
	49m 3s

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