Ensure consistent use of the local plugin dir

scripts/build_antithesis_images.sh

@@ -83,7 +83,7 @@ else
   echo "Generating compose configuration for ${TEST_SETUP}"
   gen_antithesis_compose_config "${IMAGE_TAG}" "${AVALANCHE_PATH}/tests/antithesis/xsvm/gencomposeconfig" \
                                 "${AVALANCHE_PATH}/build/antithesis/xsvm" \
-                                "AVALANCHEGO_PATH=${AVALANCHE_PATH}/build/avalanchego AVALANCHEGO_PLUGIN_DIR=${HOME}/.avalanchego/plugins"
+                                "AVALANCHEGO_PATH=${AVALANCHE_PATH}/build/avalanchego AVAGO_PLUGIN_DIR=${AVALANCHE_PATH}/build/plugins"
 
   build_antithesis_images_for_avalanchego "${TEST_SETUP}" "${IMAGE_PREFIX}" "${AVALANCHE_PATH}/vms/example/xsvm/Dockerfile"
 fi

tests/antithesis/compose.go

@@ -22,24 +22,29 @@ import (
 
 const bootstrapIndex = 0
 
+const (
+	targetPathEnvName = "TARGET_PATH"
+	imageTagEnvName   = "IMAGE_TAG"
+)
+
 var (
-	errTargetPathEnvVarNotSet = errors.New("TARGET_PATH environment variable not set")
-	errImageTagEnvVarNotSet   = errors.New("IMAGE_TAG environment variable not set")
-	errAvalancheGoEvVarNotSet = errors.New("AVALANCHEGO_PATH environment variable not set")
-	errPluginDirEnvVarNotSet  = errors.New("AVALANCHEGO_PLUGIN_DIR environment variable not set")
+	errTargetPathEnvVarNotSet = errors.New(targetPathEnvName + " environment variable not set")
+	errImageTagEnvVarNotSet   = errors.New(imageTagEnvName + " environment variable not set")
+	errAvalancheGoEvVarNotSet = errors.New(tmpnet.AvalancheGoPathEnvName + " environment variable not set")
+	errPluginDirEnvVarNotSet  = errors.New(tmpnet.AvalancheGoPluginDirEnvName + " environment variable not set")
 )
 
 // Creates docker compose configuration for an antithesis test setup. Configuration is via env vars to
 // simplify usage by main entrypoints. If the provided network includes a subnet, the initial DB state for
 // the subnet will be created and written to the target path. The runtimePluginDir should be set if the node
 // image used for the test setup uses a path other than the default (~/.avalanchego/plugins).
 func GenerateComposeConfig(network *tmpnet.Network, baseImageName string, runtimePluginDir string) error {
-	targetPath := os.Getenv("TARGET_PATH")
+	targetPath := os.Getenv(targetPathEnvName)
 	if len(targetPath) == 0 {
 		return errTargetPathEnvVarNotSet
 	}
 
-	imageTag := os.Getenv("IMAGE_TAG")
+	imageTag := os.Getenv(imageTagEnvName)
 	if len(imageTag) == 0 {
 		return errImageTagEnvVarNotSet
 	}