Fix RandomX validation exploit with difficulty reset, improve build system

- One-time difficulty reset to minimum for 17 blocks at activation height
- Separate RandomX build dirs for linux/win64 cross-compilation
- Add build target tracking to auto-clean on target switch
- Automated win64 release packaging to release-win64/
- Add build artifacts to .gitignore
- Miner memory diagnostics and large-page dataset fallback

util/build.sh

@@ -139,13 +139,13 @@ echo $PWD
 ./makecustom
 cd $WD
 
-# Build RandomX
+# Build RandomX for Linux
 cd src/RandomX
-if [ -d "build" ]
+if [ -f "build-linux/librandomx.a" ]
 then
-    ls -la build/librandomx*
+    ls -la build-linux/librandomx*
 else
-    mkdir build && cd build
+    mkdir -p build-linux && cd build-linux
     cmake -DARCH=native ..
     make
 fi