practracker scans build directories inside the tor/ directory

When I run practracker after the failed "make distcheck" in #31577 (moved), I get these errors:

problem function-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/socks5.c:socks4_client_request_encode() 352
problem function-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/socks5.c:socks4_client_request_parse_into() 332
problem function-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/socks5.c:socks5_client_request_encode() 113
problem function-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/socks5.c:socks5_server_reply_encode() 113
problem file-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/socks5.h 995
problem function-size /build-c/tor-0.4.2.0-alpha-dev/src/trunnel/hs/cell_introduce1.c:trn_cell_introduce_encrypted_encode() 110
(warning) problem file-size /src/core/or/circuitpadding.c 3096
(warning) problem function-size /src/core/or/circuitpadding.c:circpad_machine_schedule_padding() 113
(warning) problem file-size /src/core/or/circuitpadding.h 813
(warning) problem file-size /src/core/or/relay.c 3264
(warning) problem file-size /src/feature/hs/hs_service.c 4125
(warning) problem file-size /src/feature/nodelist/routerlist.c 3241
(warning) problem function-size /src/feature/rend/rendmid.c:rend_mid_establish_intro_legacy() 105
(warning) problem file-size /src/feature/rend/rendservice.c 4522
(warning) problem function-size /src/feature/rend/rendservice.c:rend_service_receive_introduction() 334
FAILURE: practracker found 482 new problem(s) in the code: see warnings above.

Please fix the problems if you can, and update the exceptions file
(../scripts/maint/practracker/./exceptions.txt) if you can't.

See doc/HACKING/HelpfulTools.md for more information on using practracker.
You can disable this message by setting the TOR_DISABLE_PRACTRACKER environment
variable.

make[1]: *** [check-best-practices] Error 226
make[1]: *** Waiting for unfinished jobs....