doc: update r-b issue template

---

Building this package twice does not produce the bit-by-bit identical result each time, making it harder to detect CI breaches. You can read more about this at https://reproducible-builds.org/ .

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Fixing bit-by-bit reproducibility also has additional advantages, such as avoiding hard-to-reproduce bugs, making content-addressed storage more effective and reducing rebuilds in such systems.

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I wanted to kindly point out that in this issue template, it would be beneficial

to replace the placeholder `<package>` with the actual, canonical name of the

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Building this package multiple times does not yield bit-by-bit identical

results, complicating the detection of Continuous Integration (CI) breaches. For

more information on this issue, visit

[reproducible-builds.org](https://reproducible-builds.org/).

Fixing bit-by-bit reproducibility also has additional advantages, such as

avoiding hard-to-reproduce bugs, making content-addressed storage more effective

and reducing rebuilds in such systems.

### Steps To Reproduce

In the following steps, replace `<package>` with the canonical name of the

package.

#### 1. Build the package

This step will build the package. Specific arguments are passed to the command

to keep the build artifacts so we can compare them in case of differences.

Execute the following command:

```

nix-build '<nixpkgs>' -A ... && nix-build '<nixpkgs>' -A ... --check --keep-failed

nix-build '<nixpkgs>' -A <package> && nix-build '<nixpkgs>' -A <package> --check --keep-failed

```

If this command completes successfully, no differences where found. However, when it ends in `error: derivation '<X>' may not be deterministic: output '<Y>' differs from '<Z>'`, you can use `diffoscope <Y> <Z>` to analyze the differences in the output of the two builds.

Or using the new command line style:

```

nix build nixpkgs#<package> && nix build nixpkgs#<package> --rebuild --keep-failed

```

#### 2. Compare the build artifacts

If the previous command completes successfully, no differences were found and

there's nothing to do, builds are reproducible.

If it terminates with the error message `error: derivation '<X>' may not be

deterministic: output '<Y>' differs from '<Z>'`, use `diffoscope` to investigate

the discrepancies between the two build outputs. You may need to add the

`--exclude-directory-metadata recursive` option to ignore files and directories

metadata (*e.g. timestamp*) differences.

```

nix run nixpkgs#diffoscopeMinimal -- --exclude-directory-metadata recursive <Y> <Z>

```

#### 3. Examine the build log

To examine the build log, use:

```

nix-store --read-log $(nix-instantiate '<nixpkgs>' -A <package>)

```

To view the build log of the build that produced the artifact in the binary cache:

Or with the new command line style:

```

nix-store --read-log $(nix-instantiate '<nixpkgs>' -A ...)

nix log $(nix path-info --derivation nixpkgs#<package>)

```

### Additional context

(please share the relevant fragment of the diffoscope output here,

and any additional analysis you may have done)

(please share the relevant fragment of the diffoscope output here, and any

additional analysis you may have done)