gclient2nix: update, fix for electron_38

Fixes error:

```
File "/nix/store/x95xf16qsvblyxgcag1fqmrsqm7px6rk-depot_tools-452fe3b/gclient_eval.py", line 643, in _convert
raise ValueError('invalid "and" operand %r (inside %r)' %
ValueError: invalid "and" operand 'checkout_riscv64' (inside 'checkout_linux and checkout_riscv64 and non_git_source')
```

pkgs/by-name/gc/gclient2nix/gclient2nix.py

···
                 },
                 **{
                 f"checkout_{arch}": True
-                for arch in ["x64", "arm64", "arm", "x86", "mips", "mips64", "ppc"]
+                for arch in ["x64", "arm64", "arm", "x86", "mips", "mips64", "ppc", "riscv64"]
                 },
             },
             "",

pkgs/by-name/gc/gclient2nix/package.nix

···
     # substitutions
     depot_tools_checkout = fetchgit {
       url = "https://chromium.googlesource.com/chromium/tools/depot_tools";
-      rev = "452fe3be37f78fbecefa1b4b0d359531bcd70d0d";
-      hash = "sha256-8IiJOm0FLa/u1Vd96tb33Ruj4IUTCeYgBpTk88znhPw=";
+      rev = "fa63ec7437108dcb3a611c6a6c5f3d96771e9581";
+      hash = "sha256-hRIwhIdRF2GbyXbpOdi/lla+/XYM+gKosoK+T+kYYu0=";
     };
 
     passthru = {