[develop2] append_compiler_executables_configuration() breaks libiconv package build

[ssrobins]

When I updated to the latest version of conan_provider.cmake, I started getting this error in a build that depends on the sdl conan package (which, in turn, depends on libiconv):

In file included from /Users/runner/.conan2/p/b/libicef1b3214fbc2a/b/src/srclib/binary-io.c:20:
In file included from /Users/runner/.conan2/p/b/libicef1b3214fbc2a/b/src/srclib/binary-io.h:22:
In file included from ./fcntl.h:56:
In file included from ./sys/types.h:39:
In file included from /Applications/Xcode_14.3.1.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS16.4.sdk/usr/include/sys/types.h:128:
/Applications/Xcode_14.3.1.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS16.4.sdk/usr/include/sys/_types/_uid_t.h:31:31: error: cannot combine with previous 'type-name' declaration specifier

I was able to reproduce it with this minimal code:

CMakeLists.txt

cmake_minimum_required(VERSION 3.24)

project(BugRepro)

find_package(Iconv REQUIRED)

conanfile.txt

[requires]
libiconv/1.17

Then run the following commands on macOS (Intel macbook, Monterey 12.6.7) in a directory with the above files:

1. conan remove libiconv -c
2. cmake -B build -S . -G Xcode -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES=conan_provider.cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_OSX_DEPLOYMENT_TARGET=11.0 -D CMAKE_OSX_ARCHITECTURES=arm64 -D CMAKE_SYSTEM_NAME=iOS

If you repeat the above steps with the call to append_compiler_executables_configuration() in conan_provider.cmake commented out, it works fine.

It'll also work fine if you omit -G Xcode and let the generator default to Makefile.

The presence of this in the generated conf seems to be the root of the problem:

tools.build:compiler_executables={"c":"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang","cpp":"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++"}

Without that, the libiconv build was finding the gcc compiler rather than clang. I think the proper thing here would be to fix libiconv to work with clang and I do plan at looking at that. But even if it's fixed, I'm wondering if this feature should not be enabled by default until the conan-center-index continuous integration is actually enforcing that it works?