qa: Remove unused option --srcdir #13188

The srcdir option was both unused and misleading; It should have been called builddir. So remove it.

What is the PATH environment variable used for in the test_framework? Can we just remove those lines entirely?

The PATH environment variable is used to give hints where executables are located. So, if someone were to set BITCOIND=bitcoin-qt ./test/functional/wallet_disable.py, the subprocess would find the executable in the qt subfolder of the build dir.

This is useful for e.g. #12873

This is useful for e.g. #12873

That PR uses BITCOIND=$(find . -name 'bitcoin-qt' -executable), which will give the path to the bitcoin-qt executable.

if someone were to set BITCOIND=bitcoin-qt ./test/functional/wallet_disable.py, the subprocess would find the executable in the qt subfolder of the build dir.

Yes, this works, but it's weirdly specific - you either set BITCOIND=bitcoind or BITCOIND=bitcoin-qt, and then it works for $BUILDIR/src/bitcoind or $BUILDDIR/src/qt/bitcoin-qt. Why don't we make BITCOIND require a full path?

It is harder to manually specify a full path than just the name, but I don't feel strongly either way.

utACK fac1e1f3b2d256d7c29b6ba06ae2acc0fbcdf0c2

utACK https://github.com/bitcoin/bitcoin/pull/13188/commits/fac1e1f3b2d256d7c29b6ba06ae2acc0fbcdf0c2 Only mention of --srcdir left is in some old release notes. "#8018 3e90fe6 Autofind rpc tests --srcdir (jonasschnelli)"

utACK fac1e1f