fix inherited GARBLE_LINK_TINY affecting regular builds

[Maremagnum]

Garble only sets its internal tiny-link environment flag when -tiny is true.
An inherited GARBLE_LINK_TINY=true can therefore leak into a normal build and
make the linker apply tiny behavior unexpectedly.

Always pass the internal flag as an explicit boolean, including false for a
normal build.

[Copilot]

Pull request overview

This PR prevents a caller-inherited GARBLE_LINK_TINY=true from accidentally enabling “tiny” linker behavior during normal (non--tiny) builds by always setting Garble’s internal linker flag explicitly for link invocations.

Changes:

• Always set GARBLE_LINK_TINY to an explicit boolean value (true/false) when invoking the patched linker.
• Add a regression test ensuring inherited GARBLE_LINK_TINY=true does not affect regular builds.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
main.go	Ensures the internal linker env var is always set to strconv.FormatBool(flagTiny) to avoid leakage from inherited environment.
testdata/script/tiny.txtar	Adds a script-level regression check that a normal build is not impacted by an inherited GARBLE_LINK_TINY=true.

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[luantak]

Is this solving an actual problem? Doesn't really seem like it.

[mvdan]

If you're setting GARBLE_LINK_TINY yourself, or other internal and undocumented GARBLE_ env vars, it's no surprise that you get weird behavior.

That said, this is a small defensive patch, so it seems fine even if no user should realistically ever need this. Remove the test case though, because we don't want to test unrealistic edge cases.