Add flag to clobber existing libraries and SYM files before building each project.

build/mac/BuildNGLayout.pl

@@ -28,6 +28,7 @@ use Moz;
 # configuration variables
 $DEBUG = 0;
 $ALIAS_SYM_FILES = $DEBUG;
+$CLOBBER_LIBS = 0;
 
 $pull{all} = 0;
 $pull{lizard} = 0;

build/mac/BuildNGLayoutDebug.pl

@@ -28,6 +28,8 @@ use Moz;
 # configuration variables
 $DEBUG = 1;
 $ALIAS_SYM_FILES = $DEBUG;
+$CLOBBER_LIBS = 1;			# turn on to clobber existing libs and .xSYM files before
+							# building each project
 
 $pull{all} = 0;
 $pull{lizard} = 0;

build/mac/NGLayoutBuildList.pm

@@ -329,6 +329,12 @@ sub BuildOneProject($$$$$)
 	my($project_dir) = $project_path;
 	$project_dir =~ s/:[^:]+$/:/;			# chop off leaf name
 
+	if ($main::CLOBBER_LIBS)
+	{
+		unlink "$project_dir$target_name";				# it's OK if these fail
+		unlink "$project_dir$target_name.xSYM";
+	}
+	
 	if ($toc_file ne "")
 	{
 		ReconcileProject("$project_path", "$project_dir$toc_file");

build/mac/TinderboxNGLayout.pl

@@ -29,6 +29,7 @@ use Moz;
 
 $DEBUG = 1;
 $ALIAS_SYM_FILES = 0;
+$CLOBBER_LIBS = 0;
 
 $pull{all} = 0;
 $pull{lizard} = 0;