Put release-build optimization back to level 3; remove windows GNU build.

The latter seems to fail permanently.

Thanks to [this contributor](https://github.com/Byron/dua-cli/commit/2dced34aef9b7beba3201e6a8b24d9a10a7b9a16#commitcomment-134405637)
for questioning the previous fix, which turned out to be incorrect.

1 files changed, 1 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index a33f8da..b9801d9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -52,7 +52,7 @@ incremental = false
 overflow-checks = false
 lto = "fat"
 codegen-units = 1
-build-override = { opt-level = 0 } # `0` (probably) needed to make release builds more stable on Windows GNU
+build-override = { opt-level = 3 }
 
 [dev-dependencies]
 pretty_assertions = "1.0.0"