[unrar] Don't use a custom struct member alignment

[FaultyRAM]

For some reason unrar's .vcxproj files specify a non-default member alignment, even though the source code already uses pack pragmas. With newer versions of the Windows SDK this actually breaks the build, as this build log snippet shows:

[...]
                     C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.22.27905\bin\HostX64\x86\CL.exe /c /Zi /nologo /W3 /WX- /diagnostics:column /O2 /Oi /Oy /D RARDLL /D UNRAR /D SILENT /D _WINDLL /D _MBCS /Gm- /EHsc /MT /Zp4 /GS /Gy /arch:IA32 /fp:precise /Zc:wchar_t /Zc:forScope /Zc:inline /GR- /Yc"rar.hpp" /Fp"build\unrardll32\Release\obj\UnRAR.pch" /Fo"build\unrardll32\Release\obj\\" /Fd"build\unrardll32\Release\obj\vc142.pdb" /Gd /TP /wd4007 /wd4996 /analyze- /FC /errorReport:queue /MP rarpch.cpp (TaskId:40)
                     Tracking command: (TaskId:40)
                     C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin\Tracker.exe /d "C:\Program Files (x86)\MSBuild\15.0\FileTracker\FileTracker32.dll" /i C:\vcpkg\buildtrees\unrar\src\unrar\build\unrardll32\Release\obj\UnRAR.tlog /r C:\VCPKG\BUILDTREES\UNRAR\SRC\UNRAR\RARPCH.CPP /b MSBuildConsole_CancelEventb780407467ca4a77a133ce5f154828e9  /c "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.22.27905\bin\HostX64\x86\CL.exe"  /c /Zi /nologo /W3 /WX- /diagnostics:column /O2 /Oi /Oy /D RARDLL /D UNRAR /D SILENT /D _WINDLL /D _MBCS /Gm- /EHsc /MT /Zp4 /GS /Gy /arch:IA32 /fp:precise /Zc:wchar_t /Zc:forScope /Zc:inline /GR- /Yc"rar.hpp" /Fp"build\unrardll32\Release\obj\UnRAR.pch" /Fo"build\unrardll32\Release\obj\\" /Fd"build\unrardll32\Release\obj\vc142.pdb" /Gd /TP /wd4007 /wd4996 /analyze- /FC /errorReport:queue /MP rarpch.cpp (TaskId:40)
                     rarpch.cpp (TaskId:40)
14:53:55.341     1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.18362.0\um\winnt.h(2482,40): error C2338:  Windows headers require the default packing option. Changing this can lead to memory corruption. This diagnostic can be disabled by building with WINDOWS_IGNORE_PACKING_MISMATCH defined. [C:\vcpkg\buildtrees\unrar\src\unrar\UnRARDll.vcxproj]
                     The command exited with code 2. (TaskId:40)
                   Done executing task "CL" -- FAILED. (TaskId:40)
[...]

I've added a patch for unrar that just deletes the <StructMemberAlignment> specifications from UnRARDll.vcxproj, which fixes the build.

[msftclas]

All CLA requirements met.

[ras0219-msft]

LGTM, thanks for the PR!