[tests] fix verbose output if TEST_VERBOSE=1, add test_examples target

Makefile

@@ -317,9 +317,12 @@ run_tests:
 
 test: all replace_current_conf_xml run_tests restore_conf_xml
 
+test_examples: all
+	CONF_XML=conf/conf_tests.xml prove tests/examples/
+
 
 .PHONY: all print_build_version _print_building _save_build_version update_google_version dox ground_segment ground_segment.opt \
 subdirs $(SUBDIRS) conf ext libpprz multimon cockpit cockpit.opt tmtc tmtc.opt generators\
 static sim_static lpctools commands \
 clean cleanspaces ab_clean dist_clean distclean dist_clean_irreversible \
-test replace_current_conf_xml run_tests restore_conf_xml
+test replace_current_conf_xml run_tests restore_conf_xml test_examples

tests/examples/01_compile_all_aircrafts.t

@@ -129,11 +129,11 @@ sub run_program
     my $stderr_and_out = '';
 
     my $stdout_handler = sub {
-        print @_ if $verbose;
+        warn @_ if $verbose;
         $stderr_and_out .= $_[0];
     };
     my $stderr_handler = sub {
-        print @_ if $verbose;
+        warn @_ if $verbose;
         # check if output on stderr contains warnings, but ignoring "Warning: low altitude"
         if ($_[0] =~ /warning/i && $_[0] !~ /Warning: low altitude/) {
             $warnings .= $_[0]."\n";