osbase/build/genosrelease: Add trailing newline to os-release

Text files should end with a newline.

Change-Id: I14f06359959a41d3a49ecfb3923cb5e509020310
Reviewed-on: https://review.monogon.dev/c/monogon/+/3592
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/osbase/build/genosrelease/main.go b/osbase/build/genosrelease/main.go
index adb8202..c4b2a79 100644
--- a/osbase/build/genosrelease/main.go
+++ b/osbase/build/genosrelease/main.go
@@ -72,7 +72,7 @@
 		fmt.Printf("Failed to encode os-release file: %v\n", err)
 		os.Exit(1)
 	}
-	if err := os.WriteFile(*flagOutFile, []byte(osReleaseContent), 0644); err != nil {
+	if err := os.WriteFile(*flagOutFile, []byte(osReleaseContent+"\n"), 0644); err != nil {
 		fmt.Printf("Failed to write os-release file: %v\n", err)
 		os.Exit(1)
 	}