File reproducible.patch of Package freerct

https://github.com/FreeRCT/FreeRCT/pull/303 

From 8a9237321c7813972ed6d76e4fa569abc24ff288 Mon Sep 17 00:00:00 2001
From: "Bernhard M. Wiedemann" <bwiedemann@suse.de>
Date: Sun, 25 Sep 2022 16:00:27 +0200
Subject: [PATCH] Allow to override build date with SOURCE_DATE_EPOCH

in order to make builds reproducible.
See https://reproducible-builds.org/ for why this is good
and https://reproducible-builds.org/specs/source-date-epoch/ for the definition of this variable.

This patch was done while working on reproducible builds for openSUSE.
---
 src/rcdgen/check_data.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/rcdgen/check_data.cpp b/src/rcdgen/check_data.cpp
index 16a4a2d5..72ad276b 100644
--- a/src/rcdgen/check_data.cpp
+++ b/src/rcdgen/check_data.cpp
@@ -11,7 +11,9 @@
 #include <map>
 #include <vector>
 #include <memory>
+#include <cstdlib>
 #include <ctime>
+#include <sstream>
 #include "ast.h"
 #include "nodes.h"
 #include "string_storage.h"
@@ -2810,6 +2812,15 @@ static std::shared_ptr<INFOBlock> ConvertINFONode(std::shared_ptr<NodeGroup> ng)
 
 	char buffer[32];
 	time_t cur_time = time(nullptr);
+	const char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+	if (source_date_epoch != nullptr) {
+		std::istringstream iss(source_date_epoch);
+		iss >> cur_time;
+		if (iss.fail() || !iss.eof()) {
+			fprintf(stderr, "Error: Cannot parse SOURCE_DATE_EPOCH as integer: %s\n", source_date_epoch);
+			cur_time = time(nullptr);
+		}
+	}
 	struct tm *now = gmtime(&cur_time);
 	strftime(buffer, lengthof(buffer), "%Y%m%dT%H%M%S", now);
 	blk->build = buffer;