From 939355f66727bb86819f90e74b25a6ed11ff5ad7 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Sun, 15 Jun 2025 08:20:48 -0700
Subject: [PATCH] tool/gocross: put the synthetic GOROOTs outside of the tsgo
 directory

We aim to make the tsgo directories be read-only mounts on builders.

But gocross was previously writing within the ~/.cache/tsgo/$HASH/
directories to make the synthetic GOROOT directories.

This moves them to ~/.cache/tsgoroot/$HASH/ instead.

Updates tailscale/corp#28679
Updates tailscale/corp#26717

Change-Id: I0d17730bbdce3d6374e79d49486826575d4690af
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
---
 tool/gocross/gocross-wrapper.sh | 1 +
 tool/gocross/toolchain.go       | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/tool/gocross/gocross-wrapper.sh b/tool/gocross/gocross-wrapper.sh
index 90f308eb5..e9fca2aea 100755
--- a/tool/gocross/gocross-wrapper.sh
+++ b/tool/gocross/gocross-wrapper.sh
@@ -74,6 +74,7 @@ case "$REV" in
             echo "# Cleaning up old Go toolchain $hash" >&2
             rm -rf "$HOME/.cache/tsgo/$hash"
             rm -rf "$HOME/.cache/tsgo/$hash.extracted"
+            rm -rf "$HOME/.cache/tsgoroot/$hash"
         done
     fi
     ;;
diff --git a/tool/gocross/toolchain.go b/tool/gocross/toolchain.go
index e701662f5..f422e289e 100644
--- a/tool/gocross/toolchain.go
+++ b/tool/gocross/toolchain.go
@@ -62,7 +62,7 @@ func getToolchain() (toolchainDir, gorootDir string, err error) {
 
 	cache := filepath.Join(os.Getenv("HOME"), ".cache")
 	toolchainDir = filepath.Join(cache, "tsgo", rev)
-	gorootDir = filepath.Join(toolchainDir, "gocross-goroot")
+	gorootDir = filepath.Join(cache, "tsgoroot", rev)
 
 	// You might wonder why getting the toolchain also provisions and returns a
 	// path suitable for use as GOROOT. Wonder no longer!