[bug] build config picks up host iconv and fails linking

[AJenbo]

Describe the bug
When building SDL2 the process will fail due to CMake seeing the host system iconv lib, and then failing to find a proper lib to link with at link time.

To Reproduce
Steps to reproduce the behavior:

1. Clone this PR Build for ios diasurgical/devilutionX#3612
2. Run the build process

Expected behavior
The build should successfully generate an iOS app.

Environment

• CMake 3.22
• https://github.com/diasurgical/devilutionX/blob/25dc2be56683cf5a9981d7041be040a346a655d3/CMakeLists.txt

[leetal]

Hi! I see that you merged the aforementioned PR. Did you solve this somehow yourself?

[AJenbo]

we endedup changing libsdl to first check for the ios specific one, and then avoid probing for the host lib if the first check fails. This isn't the most robust solution and only works out because it has another iconv implementation. If there where none and we had to fall back to SDL's own implementation this solution wouldn't have been possible.

https://github.com/libsdl-org/SDL/pull/5046/files