fix: nix build environment fixes

- flake.nix: add capnpc source override (ghfast.top proxy)
- flake.nix: add GOROOT to devShell for Go version consistency
- tools/go_build: support file:// GOPROXY for sandbox builds
- bcctool: add .gitignore for gomodcache/
- bcctool: go.mod updated by go mod download

Co-Authored-By: Claude <noreply@anthropic.com>

src/autoscaler/providers/baidu/src/bcctool/.gitignore

@@ -0,0 +1 @@
+gomodcache/

src/autoscaler/providers/baidu/src/bcctool/go.mod

@@ -4,18 +4,18 @@ go 1.22.2
 
 require (
 	github.com/baidubce/bce-sdk-go v0.9.233
+	github.com/google/uuid v1.6.0
 	github.com/xeipuuv/gojsonschema v1.2.0
 )
 
 require (
-	github.com/google/uuid v1.6.0 // indirect
 	github.com/xeipuuv/gojsonpointer v0.0.0-20180127040702-4e3ac2762d5f // indirect
 	github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415 // indirect
 )
 
 require (
 	go.uber.org/multierr v1.10.0 // indirect
-	go.uber.org/zap v1.27.0 // indirect
-	gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
+	go.uber.org/zap v1.27.0
+	gopkg.in/natefinch/lumberjack.v2 v2.2.1
 	gopkg.in/yaml.v2 v2.4.0
 )

src/flake.nix

@@ -22,6 +22,14 @@
           mypkgs = xbuild.packages.${system} // extralib.packages.${system} // librtti.packages.${system};
           overlays = [
             (final: prev: mypkgs // prev)
+            (final: prev: {
+              capnpc = prev.capnpc.overrideAttrs (oldAttrs: {
+                src = final.fetchurl {
+                  url = "https://ghfast.top/https://github.com/shen390s/c-capnproto/archive/e45ff682c4756ac5067cbac6d0f282a8ea5f0155.tar.gz";
+                  hash = "sha256-zsiX6unPF45eISP6sqbQImrivJuSE0BF4bTP/db+lQY=";
+                };
+              });
+            })
           ];
           pkgs = import nixpkgs { inherit overlays system;};
           xpkgs = import ./nixSupport/default.nix {
@@ -58,6 +66,7 @@
           defaultPackage = xpkgs.xcecore_debug;
           devShells.default = pkgs.mkShell {
             nativeBuildInputs = xpkgs.xcecore.nativeBuildInputs;
+            GOROOT = "${pkgs.go}/share/go";
           };
 
           devShell = self.devShells.${system}.default;

src/tools/go_build

@@ -99,4 +99,9 @@ done
 
 export GOPROXY=https://goproxy.cn
 
+# Use pre-downloaded Go module cache if available (avoids network inside sandbox)
+if [ -d "$_sdir/gomodcache/pkg/mod/cache/download" ]; then
+    export GOPROXY="file://${_sdir}/gomodcache/pkg/mod/cache/download,off"
+fi
+
 (cd $_sdir; go build -gcflags "all=-N -l" -o "$_dfile" "$_sfile")