[gettext] Remove SUBPATH, add iconv linking info

[dg0yt]

• What does your PR fix?

  • Replaces the SUBPATH argument to vcpkg_build_make, as discussed in [scripts-audit] Make buildsystem (port) #19753 (CC @JackBoosY)
  • Adds Iconv_LIBRARIES to Intl_LIBRARIES in Intl wrapper, as discussed in [kf5package] new port #19195 (CC @wrobelda)
    Reverts the kf5i18n patching for the gettext -> iconv dependency which is now handled in gettext ([gettext] Remove SUBPATH, add iconv linking info #20090 (comment)). (kf5i18n doesn't use FindIntl.cmake.)
  • Fixes mingw-dynamic builds (from upstream).

• Which triplets are supported/not supported? Have you updated the CI baseline?

  all, no
  Tested locally in x64-mingw-static cross build.

• Does your PR follow the maintainer guide?

  yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  yes

[JackBoosY]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[wrobelda]

@dg0yt can you also remove the libiconv patch from kf5i18n? It would test this PR nicely, given that many other kf5 ports depend on libiconv in kf5i18n, see e.g. #19195 (comment) or #19766 (comment).

[JackBoosY]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[dg0yt]

@dg0yt can you also remove the libiconv patch from kf5i18n? It would test this PR nicely, given that many other kf5 ports depend on libiconv in kf5i18n, see e.g. #19195 (comment) or #19766 (comment).

@wrobelda I have to revert the related change. The issue is that kf5i18n doesn't use the wrapped FindIntl.cmake but maintains its own FindLibIntl.cmake.

[BillyONeal]

Thanks for the bugfix!