GPU: Un-hardcode /bin/bash location

[HeroBrine1st]

What I tested

• Verified no regressions to existing functionality.
  It is assumed there's no side-effects in this change, so I did no regression tests as they're not needed.
• Tested on the following Gnome Shell versions: 45.5, 46.1

Changes

This PR changes hardcoded /bin/bash to /usr/bin/env bash in GPU module, fixing non-working GPU module for non-FHS distributions such as NixOS.

Actually tested with direct patch to NixOS package, but this PR is so small it doesn't need throrough testing.

The NixOS override I use for now

{gnomeExtensions}: gnomeExtensions.system-monitor-next.overrideAttrs (old: {
  patches = old.patches ++ [
    ./usr-bin-env.patch
  ];
})

Mentioned patch is (the same as in this PR):

--- a/extension.js
+++ b/extension.js
@@ -2161,7 +2161,7 @@ const Gpu = class SystemMonitor_Gpu extends ElementBase {
         // Run asynchronously, to avoid shell freeze
         try {
             let path = this.extension.path;
-            let script = ['/bin/bash', path + '/gpu_usage.sh'];
+            let script = ['/usr/bin/env', 'bash', path + '/gpu_usage.sh'];

             // Create subprocess and capture STDOUT
             let proc = new Gio.Subprocess({argv: script, flags: Gio.SubprocessFlags.STDOUT_PIPE});

Also tested this patch on Arch Linux (FHS distribution) - GPU module works as expected.

Warning: I did not test this patch on master branch, I did only on latest (66) version from e.g.o

---

This change is 

[HeroBrine1st]

Another (and probably better) option is to not use /bin/bash in command and instead place it in shebang. /bin/sh is already there and is actually patched by nix builder, but I don't think zip tarball can include file permissions, so it would be a regression for e.g.o users.

[HeroBrine1st]

I forgot to check other PRs. This PR conflicts with #71, but those two can be easily merged as both are small. IDK how to make a PR that depends on another PR so I leave this as-is.

If you want me to merge this with #71, just tell me.

[mgalgs]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @HeroBrine1st)

[mgalgs]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @HeroBrine1st)