fix bunx on windows with postinstall scripts

[RiskyMH]

fixes #9841
_{fixes #15783, fixes #15562, fixes #14848, fixes #12336, fixes #10068}

context behind change is it runs <current-exe> exec on windows which would be bunx exec but as that subcommand wasn't resolvable it just tried to run exec as a package:

bun/src/install/lifecycle_script_runner.zig

Lines 166 to 176 in 1ccc13e

	var argv = if (shell_bin != null and !Environment.isWindows) [_]?[*:0]const u8{
	shell_bin.?,
	"-c",
	combined_script,
	null,
	} else [_]?[*:0]const u8{
	try bun.selfExePath(),
	"exec",
	combined_script,
	null,
	};

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will try to add tests which fail without this

[robobun]

^{Updated 9:40 PM PT - Feb 5th, 2025}

❌ @RiskyMH, your commit 5fe203d has 1 failures in Build #11177:

• test/js/bun/http/serve-body-leak.test.ts - 5 failing on 🐧 3.20 x64

---

🧪   try this PR locally:

bunx bun-pr 17076

[hakimio]

Maybe there should be some test for this?

[RiskyMH]

will try to add tests which fail without this

Yeah i will. Just investigating more rn. Also going to sleep soon, but I wanted to find the cause of this as it was buging me.

Seems simple to add test though, im surprised it hasn't failed anything already but the tests probably don't have bunx simlink and instead rely on effectively bun x.

[dylan-conway]

Looks good. @paperclover should take a look too

[paperclover]

great find