[qtdeclarative] Fix post-build check problem

Fixes #38720. After installing qtsvg, a post-build check problem will occur when installing qtdeclarative. Fix it here:

-- Performing post-build validation
warning: The following EXEs were found in /bin or /debug/bin. EXEs are not valid distribution targets.

  E:\all\vcpkg\packages\qtdeclarative_x64-windows-release\bin\svgtoqml.exe

error: Found 1 post-build check problem(s). To submit these ports to curated catalogs, please first correct the portfile: E:\all\vcpkg\ports\qtdeclarative\portfile.cmake

[x] Changes comply with the maintainer guide.
[ ] ~SHA512s are updated for each updated download.~
[ ] ~The "supports" clause reflects platforms that may be fixed by this new version.~
[ ] ~Any fixed CI baseline entries are removed from that file.~
[ ] ~Any patches that are no longer applied are deleted from the port's directory.~
[x] The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
[x] Only one version is added to each modified port's versions file.

microsoft / vcpkg

[qtdeclarative] Fix post-build check problem #38738