Switch build system to rolling releases.

src/host/buildvm.c

@@ -320,6 +320,7 @@ static void emit_vmdef(BuildCtx *ctx)
   char buf[80];
   int i;
   fprintf(ctx->fp, "-- This is a generated file. DO NOT EDIT!\n\n");
+  fprintf(ctx->fp, "assert(require(\"jit\").version == \"%s\", \"LuaJIT core/library version mismatch\")\n\n", LUAJIT_VERSION);
   fprintf(ctx->fp, "module(...)\n\n");
 
   fprintf(ctx->fp, "bcnames = \"");

src/host/genversion.lua

@@ -0,0 +1,43 @@
+----------------------------------------------------------------------------
+-- Lua script to embed the rolling release version in luajit.h.
+----------------------------------------------------------------------------
+-- Copyright (C) 2005-2023 Mike Pall. All rights reserved.
+-- Released under the MIT license. See Copyright Notice in luajit.h
+----------------------------------------------------------------------------
+
+local FILE_INPUT_H = "luajit_rolling.h"
+local FILE_INPUT_R = "luajit_relver.txt"
+local FILE_OUTPUT_H = "luajit.h"
+
+local function file_read(file)
+  local fp = assert(io.open(file, "rb"), "run from the wrong directory")
+  local data = assert(fp:read("*a"))
+  fp:close()
+  return data
+end
+
+local function file_write_mod(file, data)
+  local fp = io.open(file, "rb")
+  if fp then
+    local odata = assert(fp:read("*a"))
+    fp:close()
+    if odata == data then return end
+  end
+  fp = assert(io.open(file, "wb"))
+  assert(fp:write(data))
+  assert(fp:close())
+end
+
+local text = file_read(FILE_INPUT_H)
+local relver = file_read(FILE_INPUT_R):match("(%d+)")
+
+if relver then
+  text = text:gsub("ROLLING", relver)
+else
+  io.stderr:write([[
+**** WARNING Cannot determine rolling release version from git log.
+**** WARNING The 'git' command must be available during the build.
+]])
+end
+
+file_write_mod(FILE_OUTPUT_H, text)