newt: disable parallel build

The newt build system contains a race condition, which sometimes breaks
the build with high BR2_JLEVEL settings.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/newt/newt.mk

@@ -42,7 +42,7 @@ $(NEWT_DIR)/.configured: $(NEWT_DIR)/.source
 	touch $(NEWT_DIR)/.configured
 
 $(NEWT_DIR)/libnewt.so.$(NEWT_VERSION): $(NEWT_DIR)/.configured
-	$(MAKE) CFLAGS="$(TARGET_CFLAGS) $(NEWT_CFLAGS)" CC="$(TARGET_CC)" -C $(NEWT_DIR)
+	$(MAKE1) CFLAGS="$(TARGET_CFLAGS) $(NEWT_CFLAGS)" CC="$(TARGET_CC)" -C $(NEWT_DIR)
 	touch -c $@
 
 $(STAGING_DIR)/usr/lib/libnewt.a: $(NEWT_DIR)/libnewt.so.$(NEWT_VERSION)