Document choice of script exit code

tests/scripts/curves.pl

@@ -36,6 +36,7 @@ my @curves = split( /\s+/, `sed -n -e '$sed_cmd' $config_h` );
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }

tests/scripts/depends-hashes.pl

@@ -45,6 +45,7 @@ my @hashes = split( /\s+/,
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }

tests/scripts/depends-pkalgs.pl

@@ -60,6 +60,7 @@ my %algs = (
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }

tests/scripts/key-exchanges.pl

@@ -33,6 +33,7 @@ my @kexes = split( /\s+/, `sed -n -e '$sed_cmd' $config_h` );
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }

tests/scripts/test-ref-configs.pl

@@ -43,6 +43,7 @@ my $config_h = 'include/mbedtls/config.h';
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }