I assume you've downloaded
https://github.com/bitcoin/bitcoin, just search for the hash eternalgloom mentioned. Quick and dirty, but it works:
bitcoin-master $ for i in `find`; do grep 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f $i 2> /dev/null; done
settings['genesis'] = '000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f'
genesis=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
src/bitcoin-cli -named getblock blockhash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
Or, if you want to see which files contain these lines:
bitcoin-master $ for i in `find`; do if [ -n "`grep 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f $i 2> /dev/null`" ]; then echo $i; fi; done
./contrib/linearize/linearize-data.py
./contrib/linearize/example-linearize.cfg
./src/chainparams.cpp
./doc/release-notes/release-notes-0.14.0.md