build: Specify exec argument for TAP::Harness

Older versions of TAP::Harness do not handle non-perl executables. So
check if the test has the executable bits, and return an arrayref to
use it, otherwise return undef to use the perl interpreter.

check.am

@@ -14,6 +14,8 @@ TEST_PARALLEL ?= 1
 
 TEST_RUNNER = '\
 	my $$harness = TAP::Harness->new({ \
+	    exec => sub { my (undef, $$test) = @_; \
+	                  return -x $$test ? [ $$test ] : undef }, \
 	    lib => [ "$(top_srcdir)/scripts", "$(top_srcdir)/dselect/methods"  ], \
 	    color => 1, \
 	    verbosity => $(TEST_VERBOSE), \

debian/changelog

@@ -17,6 +17,8 @@ dpkg (1.18.11) UNRELEASED; urgency=medium
       when some unrelated warning needs to be emitted.
     - Bump po4a version to 0.43 (we are using --porefs wrap option).
     - Add support for running the test suite in parallel.
+    - Specify exec argument for TAP::Harness to gracefully handle non-perl
+      executables with older versions of the module.
 
   [ Updated manpages translations ]
   * German (Helge Kreutzmann).