From ca8b670eac0b0def66249738e52ef8137d30a8b5 Mon Sep 17 00:00:00 2001
From: Jiuyang Liu
Date: Sun, 4 Apr 2021 13:32:20 +0800
Subject: Fix mill cache download (#2171)

---
 build.sc | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/build.sc b/build.sc
index 4ac60a51..ec154b89 100644
--- a/build.sc
+++ b/build.sc
@@ -97,7 +97,9 @@ class firrtlCrossModule(val crossScalaVersion: String) extends CrossSbtModule wi
   }
 
   def downloadAntlr4Jar = T.persistent {
-    Util.download(s"https://www.antlr.org/download/antlr-$antlr4Version-complete.jar")
+    if (!os.isFile( T.ctx.dest / "antlr4" ))
+      Util.download(s"https://www.antlr.org/download/antlr-$antlr4Version-complete.jar", os.rel / "antlr4")
+    PathRef(T.ctx.dest / "antlr4")
   }
 
   def generatedAntlr4Source = T.sources {
@@ -155,16 +157,20 @@ class firrtlCrossModule(val crossScalaVersion: String) extends CrossSbtModule wi
         else throw new Exception("mill cannot detect your architecture of your Windows")
       else throw new Exception("mill cannot detect your operation system.")
 
-    val zip = Util.downloadUnpackZip(
-      s"https://github.com/protocolbuffers/protobuf/releases/download/v$protocVersion/protoc-$protocVersion-$protocBinary.zip"
-    )
+    val unpackPath = os.rel / "unpacked"
+
     val bin = if(isWindows)
-      zip.path / "bin" / "protoc.exe"
+      T.ctx.dest / unpackPath / "bin" / "protoc.exe"
     else
-      zip.path / "bin" / "protoc"
+      T.ctx.dest / unpackPath / "bin" / "protoc"
 
+    if (!os.exists(bin))
+      Util.downloadUnpackZip(
+        s"https://github.com/protocolbuffers/protobuf/releases/download/v$protocVersion/protoc-$protocVersion-$protocBinary.zip",
+        unpackPath
+      )
     // Download Linux/Mac binary doesn't have x.
-    if (!isWindows) os.perms.set(bin, "--x------")
+    if (!isWindows) os.perms.set(bin, "rwx------")
     PathRef(bin)
   }
 
-- 
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