When called by 'make check', the test suite runs with a MAKEFLAGS
variable in environment which defines TEST_LOGS variable with the test
suites' corresponding logs as value. This in turn causes the called
'make distcheck' to run test suites although it is not supposed to.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 tests/build/run-tests.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/build/run-tests.sh b/tests/build/run-tests.sh
index a5e026a97dd5b..80fa10168d003 100755
--- a/tests/build/run-tests.sh
+++ b/tests/build/run-tests.sh
@@ -20,6 +20,10 @@ fi
 git clone "$dir" "$tmpdir" &>>"$log_file"
 cd "$tmpdir" || exit
 
+# do not leak data from a calling 'make check' run into the new build otherwise
+# this will defeat the test suite invocation prevention for 'make distcheck'
+unset MAKEFLAGS
+
 if ! autoreconf -fi &>>"$log_file" ; then
 	echo "Something went wrong. Check the log '${log_file}' for details."
 	exit 1
-- 
2.51.0