version: return correct Meta.MajorMinorPatch in non-dev builds

Signed-off-by: David Anderson <danderson@tailscale.com>

version-embed.go

@@ -6,8 +6,13 @@ package tailscaleroot
 
 import _ "embed"
 
+// VersionDotTxt is the contents of VERSION.txt. Despite the tempting filename,
+// this does not necessarily contain the accurate version number of the build, which
+// depends on the branch type and how it was built. To get version information, use
+// the version package instead.
+//
 //go:embed VERSION.txt
-var Version string
+var VersionDotTxt string
 
 //go:embed ALPINE.txt
 var AlpineDockerTag string