add variable to build with TARGET_CARBON. Off for now, but can be turned on by anyone wanting to build Carbon.

build/mac/BuildNGLayout.pl

@@ -30,6 +30,7 @@ $DEBUG = 0;
 $ALIAS_SYM_FILES = $DEBUG;
 $CLOBBER_LIBS = 1;
 $MOZ_FULLCIRCLE = 0;
+$CARBON = 0;				# turn on to build with TARGET_CARBON
 
 # The following two options will delete all files, but leave the directory structure intact.
 $CLOBBER_DIST_ALL = 0;      # turn on to clobber all files inside dist (headers, xsym and libs)

build/mac/BuildNGLayoutDebug.pl

@@ -30,6 +30,7 @@ $DEBUG = 1;
 $ALIAS_SYM_FILES = $DEBUG;
 $CLOBBER_LIBS = 1;			# turn on to clobber existing libs and .xSYM files before
 							# building each project
+$CARBON = 0;				# turn on to build with TARGET_CARBON
 							
 # The following two options will delete all files, but leave the directory structure intact.
 $CLOBBER_DIST_ALL = 0;      # turn on to clobber all aliases/files inside dist (headers/xsym/libs)