Fix config format outputted by preinstall script (#1149)

Author: dhurley

go.mod

@@ -66,6 +66,7 @@ require (
 	go.opentelemetry.io/collector/processor v1.30.0
 	go.opentelemetry.io/collector/processor/batchprocessor v0.124.0
 	go.opentelemetry.io/collector/processor/memorylimiterprocessor v0.124.0
+	go.opentelemetry.io/collector/processor/processortest v0.124.0
 	go.opentelemetry.io/collector/receiver v1.30.0
 	go.opentelemetry.io/collector/receiver/otlpreceiver v0.124.0
 	go.opentelemetry.io/collector/receiver/receivertest v0.124.0
@@ -74,6 +75,7 @@ require (
 	go.opentelemetry.io/collector/scraper/scrapertest v0.124.0
 	go.opentelemetry.io/otel v1.35.0
 	go.uber.org/goleak v1.3.0
+	go.uber.org/multierr v1.11.0
 	go.uber.org/zap v1.27.0
 	golang.org/x/mod v0.23.0
 	golang.org/x/sync v0.13.0
@@ -260,7 +262,6 @@ require (
 	go.opentelemetry.io/collector/pipeline/xpipeline v0.124.0 // indirect
 	go.opentelemetry.io/collector/processor/processorhelper v0.124.0 // indirect
 	go.opentelemetry.io/collector/processor/processorhelper/xprocessorhelper v0.124.0 // indirect
-	go.opentelemetry.io/collector/processor/processortest v0.124.0 // indirect
 	go.opentelemetry.io/collector/processor/xprocessor v0.124.0 // indirect
 	go.opentelemetry.io/collector/receiver/receiverhelper v0.124.0 // indirect
 	go.opentelemetry.io/collector/receiver/xreceiver v0.124.0 // indirect
@@ -289,7 +290,6 @@ require (
 	go.opentelemetry.io/otel/sdk/log v0.11.0 // indirect
 	go.opentelemetry.io/otel/trace v1.35.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.5.0 // indirect
-	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/arch v0.12.0 // indirect
 	golang.org/x/exp v0.0.0-20250210185358-939b2ce775ac // indirect
 	golang.org/x/tools v0.30.0 // indirect

scripts/packages/preinstall.sh

@@ -130,8 +130,13 @@ command:
         skip_verify: false
 "
 
-        echo "$v3_config_contents" > "$v3_config_file" \
-            || err_exit "Failed to write v3 config"
+        if [ -n "$( echo -e )" ]; then
+            echo "$v3_config_contents" > "$v3_config_file" \
+                || err_exit "Failed to write v3 config"
+        else
+            echo -e "$v3_config_contents" > "$v3_config_file" \
+                || err_exit "Failed to write v3 config"
+        fi
     else
         echo "Existing NGINX Agent version is not v2, skipping config migration"
     fi