build: add temporary fix for "bad magic number" error in out-of-tree builds

This was caused by an pyc files hanging around from previous
python2 invocations, when the matching .py missing from that path.

This should not be a problem with python3's tagged caches.

Makefile.am

@@ -224,6 +224,9 @@ EXTRA_DIST = $(top_srcdir)/share/genbuild.sh qa/pull-tester/rpc-tests.py qa/rpc-
 
 CLEANFILES = $(OSX_DMG) $(BITCOIN_WIN_INSTALLER)
 
+# This file is problematic for out-of-tree builds if it exists.
+DISTCLEANFILES = qa/pull-tester/tests_config.pyc
+
 .INTERMEDIATE: $(COVERAGE_INFO)
 
 clean-local:

src/Makefile.test.include

@@ -123,6 +123,9 @@ CLEAN_BITCOIN_TEST = test/*.gcda test/*.gcno $(GENERATED_TEST_FILES)
 
 CLEANFILES += $(CLEAN_BITCOIN_TEST)
 
+# This file is problematic for out-of-tree builds if it exists.
+DISTCLEANFILES += test/buildenv.pyc
+
 bitcoin_test: $(TEST_BINARY)
 
 bitcoin_test_check: $(TEST_BINARY) FORCE