Permission denied opening libiconv.dll

[Blacksmoke16]

Got some Windows nightly CI failures starting somewhere between c0270c6 and 72aea71: https://github.com/athena-framework/athena/actions/runs/7982635580/job/21799257710

Error opening file with mode 'wb': 'C:\\Users\\runneradmin\\AppData\\Local\\crystal\\cache\\libiconv.dll': Permission denied (File::AccessDeniedError)
           from D:\a\crystal\crystal\src\crystal\system\win32\file.cr:24 in 'open'
           from D:\a\crystal\crystal\src\file.cr:162 in 'new'
           from D:\a\crystal\crystal\src\file.cr:725 in 'copy'
           from D:\a\crystal\crystal\src\file_utils.cr:94 in 'cp'
           from D:\a\crystal\crystal\src\compiler\crystal\compiler.cr:368 in 'copy_dlls'
           from D:\a\crystal\crystal\src\compiler\crystal\compiler.cr:335 in 'codegen'
           from D:\a\crystal\crystal\src\compiler\crystal\compiler.cr:204 in 'compile:combine_rpath'
           from D:\a\crystal\crystal\src\compiler\crystal\compiler.cr:197 in 'compile:combine_rpath'
           from D:\a\crystal\crystal\src\compiler\crystal\command.cr:360 in 'compile'
           from D:\a\crystal\crystal\src\compiler\crystal\command.cr:239 in 'run_command'
           from D:\a\crystal\crystal\src\compiler\crystal\command.cr:112 in 'run'
           from D:\a\crystal\crystal\src\compiler\crystal\command.cr:55 in 'run'
           from D:\a\crystal\crystal\src\compiler\crystal\command.cr:54 in 'run'
           from D:\a\crystal\crystal\src\compiler\crystal.cr:11 in '__crystal_main'
           from D:\a\crystal\crystal\src\crystal\main.cr:129 in 'main_user_code'
           from D:\a\crystal\crystal\src\crystal\main.cr:115 in 'main'
           from D:\a\crystal\crystal\src\crystal\main.cr:141 in 'main'
           from D:\a\crystal\crystal\src\crystal\system\win32\wmain.cr:37 in 'wmain'
           from D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288 in '__scrt_common_main_seh'
           from C:\Windows\System32\KERNEL32.DLL +8[51](https://github.com/athena-framework/athena/actions/runs/7982635580/job/21799257710#step:6:55)68 in 'BaseThreadInitThunk'
           from C:\Windows\SYSTEM32\ntdll.dll +518315 in 'RtlUserThreadStart'
         Error: you've found a bug in the Crystal compiler. Please open an issue, including source code that will allow us to reproduce the bug: https://github.com/crystal-lang/crystal/issues

Maybe related to #14292?

[HertzDevil]

To reproduce on 1.11 stable:

# foo.cr
# run with `crystal run -Dpreview_dll foo.cr`
`crystal run -Dpreview_dll #{__DIR__}\\bar.cr`

# bar.cr

Essentially, the compiler is trying to copy a DLL to the cache directory while another temporary process is already running there. You are seeing this in the latest nightly because -Dpreview_dll is now the default behavior.