moz: do not try to get into non-existent directory and ignore error

moz/makefile.mk

@@ -184,7 +184,7 @@ MOZ_CROSSCOMPILE=CROSS_COMPILE=1 CC="$(CC) -arch $(MOZ_ARCH)" CXX="$(CXX) -arch
 
 CONFIGURE_ACTION=$(null,$(MOZ_ARCH) $(NULL) $(MOZ_CROSSCOMPILE)) ../configure $(MOZILLA_CONFIGURE_FLAGS)
 
-BUILD_ACTION:=cd mozilla/X_objdir/xpcom ; $(GNUMAKE) -j$(EXTMAXPROCESS)
+BUILD_ACTION:=$(GNUMAKE) -j$(EXTMAXPROCESS)
 
 .IF "$(GUI)"=="UNX"
 .IF "$(COMNAME)"=="sunpro5"