From 6e64c14ce917805bdbd4bfe3595fc111892395fe Mon Sep 17 00:00:00 2001
From: Po Hu <po.hu@mediatek.com>
Date: Tue, 9 Mar 2021 10:48:37 +0800
Subject: [PATCH] Fix kati regen due to build_number.txt

Do NOT touch build_number.txt if BUILD_NUMBER is explicitly set
but not changed from last build.

Bug: 182221512
Test: BUILD_NUMBER=123 m nothing
Change-Id: Ic88f6e0d2b9767d84e1ec5c826018d1ea08c0fc0
---
 core/main.mk | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/main.mk b/core/main.mk
index efa6031222..2291740c16 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -41,7 +41,12 @@ include $(BUILD_SYSTEM)/clang/config.mk
 # without changing the command line every time.  Avoids rebuilds
 # when using ninja.
 $(shell mkdir -p $(SOONG_OUT_DIR) && \
-    echo -n $(BUILD_NUMBER) > $(SOONG_OUT_DIR)/build_number.txt)
+    echo -n $(BUILD_NUMBER) > $(SOONG_OUT_DIR)/build_number.tmp; \
+    if ! cmp -s $(SOONG_OUT_DIR)/build_number.tmp $(SOONG_OUT_DIR)/build_number.txt; then \
+        mv $(SOONG_OUT_DIR)/build_number.tmp $(SOONG_OUT_DIR)/build_number.txt; \
+    else \
+        rm $(SOONG_OUT_DIR)/build_number.tmp; \
+    fi)
 BUILD_NUMBER_FILE := $(SOONG_OUT_DIR)/build_number.txt
 .KATI_READONLY := BUILD_NUMBER_FILE
 $(KATI_obsolete_var BUILD_NUMBER,See https://android.googlesource.com/platform/build/+/master/Changes.md#BUILD_NUMBER)