changed $CLOBBER_LIBS from 0 to 1 [existing libs must be deleted before new one gets built]

build/mac/TinderboxNGLayout.pl

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

build/mac/TinderboxNGLayoutOpt.pl

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