Enabling LTO makes some tests fail on Windows

[fpoli]

By enabling LTO, as done in PR #372, cargo test --release fails on Windows.

Failing tests:

failures:
    [run-pass] pass\equality\pure-post-1.rs
    [run-pass] pass\equality\pure-post-2.rs
    [run-pass] pass\equality\pure-post-3.rs
    [run-pass] pass\equality\pure-post-5.rs
    [run-pass] pass\equality\pure-pre-1.rs

Error message:

error: compilation failed!
status: exit code: 0xc0000005
command: PATH=";D:\a\prusti-dev\prusti-dev\target\release\build\libgit2-sys-2a53def2b654a39b\out\build;D:\a\prusti-dev\prusti-dev\target\release\build\libssh2-sys-171e592df78b697b\out\build;D:\a\prusti-dev\prusti-dev\target\release\build\libz-sys-01c56314b1d05996\out\build;D:\a\prusti-dev\prusti-dev\target\release\build\ring-dd3bc0163d5b0b42\out;D:\a\prusti-dev\prusti-dev\target\release\deps;D:\a\prusti-dev\prusti-dev\target\release;C:\Rust\.rustup\toolchains\nightly-2021-02-01-x86_64-pc-windows-msvc\lib\rustlib\x86_64-pc-windows-msvc\lib;C:\Users\runneradmin\.cargo\bin;C:\Users\runneradmin\.rustup\toolchains\nightly-2021-02-01-x86_64-pc-windows-msvc\bin;C:\Program Files\PowerShell\7;C:\hostedtoolcache\windows\jdk\15.0.2\x64\bin;C:\Users\runneradmin\AppData\Roaming\Python\Python39\Scripts;C:\hostedtoolcache\windows\Python\3.9.1\x64\Scripts;C:\hostedtoolcache\windows\Python\3.9.1\x64;C:\Users\runneradmin\.dotnet\tools;C:\Program Files\MongoDB\Server\4.4\bin;C:\aliyun-cli;C:\ProgramData\kind;C:\vcpkg;C:\cf-cli;C:\Program Files (x86)\NSIS\;C:\Program Files\Mercurial\;C:\hostedtoolcache\windows\stack\2.5.1\x64;C:\ProgramData\chocolatey\lib\ghc.8.10.3\tools\ghc-8.10.3\bin;C:\Program Files\dotnet;C:\mysql-5.7.21-winx64\bin;C:\Program Files\R\R-4.0.3\bin\x64;C:\SeleniumWebDrivers\GeckoDriver;C:\Program Files (x86)\sbt\bin;C:\Rust\.cargo\bin;C:\Program Files (x86)\GitHub CLI;C:\Program Files\Git\bin;C:\Program Files (x86)\pipx_bin;C:\hostedtoolcache\windows\go\1.14.14\x64\bin;C:\hostedtoolcache\windows\Python\3.7.9\x64\Scripts;C:\hostedtoolcache\windows\Python\3.7.9\x64;C:\hostedtoolcache\windows\Ruby\2.5.8\x64\bin;C:\Program Files\Java\jdk8u282-b08\bin;C:\npm\prefix;C:\Program Files\Microsoft SDKs\Azure\Azure Dev Spaces CLI;C:\Program Files\Microsoft SDKs\Azure\Azure Dev Spaces CLI\;C:\Program Files (x86)\Microsoft SDKs\Azure\CLI2\wbin;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;C:\windows\System32\OpenSSH\;C:\ProgramData\Chocolatey\bin;C:\Program Files\Microsoft\Web Platform Installer\;C:\Program Files\Docker;C:\Program Files\PowerShell\7\;C:\Program Files\dotnet\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\170\Tools\Binn\;C:\Program Files (x86)\Windows Kits\10\Windows Performance Toolkit\;C:\Program Files (x86)\Microsoft SQL Server\110\DTS\Binn\;C:\Program Files (x86)\Microsoft SQL Server\120\DTS\Binn\;C:\Program Files (x86)\Microsoft SQL Server\130\DTS\Binn\;C:\Program Files (x86)\Microsoft SQL Server\140\DTS\Binn\;C:\Program Files (x86)\Microsoft SQL Server\150\DTS\Binn\;C:\Program Files\nodejs\;C:\ProgramData\chocolatey\lib\pulumi\tools\Pulumi\bin;C:\ProgramData\chocolatey\lib\maven\apache-maven-3.6.3\bin;C:\Program Files\Microsoft Service Fabric\bin\Fabric\Fabric.Code;C:\Program Files\Microsoft SDKs\Service Fabric\Tools\ServiceFabricLocalClusterManager;C:\Program Files\OpenSSL\bin;C:\Strawberry\c\bin;C:\Strawberry\perl\site\bin;C:\Strawberry\perl\bin;C:\Program Files\Git\cmd;C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\bin;c:\tools\php;C:\Program Files (x86)\sbt\bin;C:\Program Files\TortoiseSVN\bin;C:\SeleniumWebDrivers\ChromeDriver\;C:\SeleniumWebDrivers\EdgeDriver\;C:\Program Files\CMake\bin;C:\Program Files\Amazon\AWSCLIV2\;C:\Program Files\Amazon\SessionManagerPlugin\bin\;C:\Program Files\Amazon\AWSSAMCLI\bin\;C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin;C:\Program Files (x86)\Microsoft BizTalk Server\;C:\Users\runneradmin\AppData\Local\Microsoft\WindowsApps;C:\hostedtoolcache\windows\jdk\15.0.2\x64\bin\server" "..\\target\\release\\prusti-rustc.exe" "tests\\verify\\pass\\equality\\pure-pre-1.rs" "-L" "C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\" "--target=x86_64-pc-windows-msvc" "--error-format" "json" "-C" "prefer-dynamic" "-o" "C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\equality\\pure-pre-1.stage-id.exe" "--color=never" "--edition=2018" "-A" "warnings" "-L" "C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\equality\\pure-pre-1.stage-id.aux"
stdout:
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stderr:
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FAILED