aws-sam-cli: add argument to conditionally enable telemetry

If someone really wants to opt into telemetry, they can do so by setting
`enableTelemetry` to `true` (the default is `false`), in which case the wrapper
that sets `SAM_CLI_TELEMETRY` to `0` will not be created.

Note that this actually allows a user to optionally disable telemetry from the
command line or the (poorly documented) configuration in
`~/.aws-sam/metadata.json`. The downside is telemetry will be enabled at least
on the first run, causing a unique installation ID to be saved in the
configuration file.

pkgs/development/tools/aws-sam-cli/default.nix

@@ -1,5 +1,6 @@
 { lib
 , python
+, enableTelemetry ? false
 }:
 
 let
@@ -83,7 +84,7 @@ buildPythonApplication rec {
     tomlkit
   ];
 
-  postFixup = ''
+  postFixup = if enableTelemetry then "echo aws-sam-cli TELEMETRY IS ENABLED" else ''
     # Disable telemetry: https://github.com/awslabs/aws-sam-cli/issues/1272
     wrapProgram $out/bin/sam --set  SAM_CLI_TELEMETRY 0
   '';