Update autopkgtest for more upstream tests

Cherry-picked from debian/26.1-2-6-g9e15e68 ("Update autopkgtest for
more upstream tests")

debian/tests/run-testsuite

@@ -5,6 +5,8 @@ set -x
 
 cd src/testsuite
 
+export srcdir='.'
+
 cp /usr/sbin/ngircd T-ngircd1
 cp /usr/sbin/ngircd T-ngircd2
 cp /usr/sbin/ngircd T-ngircd3