Bugfix: change GNU triplet for iOS, watchOS, tvOS to allow simulator builds

[SSE4]

closes: #6428

Changelog: Bugfix: Change GNU triplet for iOS, watchOS, tvOS to allow simulator builds.
Docs: Omit

the issue came up several times in the past already, e.g.
conan-io/conan-center-index#1008 (comment)
bincrafters/conan-libiconv#11

currently, recipes use the following ugly workaround:
https://github.com/conan-io/conan-center-index/blob/8110cdeccead2f2d37fcea22919fe5d18f58d833/recipes/libiconv/all/conanfile.py#L106
https://github.com/conan-io/conan-center-index/blob/8110cdeccead2f2d37fcea22919fe5d18f58d833/recipes/libcurl/all/conanfile.py#L367

            if self.settings.os == "iOS" and self.settings.arch == "x86_64":
                # please do not autodetect --build for the iOS simulator, thanks!

changes were tested locally on libiconv and libcurl

old triplet for iOS simulator was x86_64-apple-darwin (same as MacOS, which confused auto-tools configure scripts).
the new deduced triplet is x86_64-apple-ios.
sources:
LLVM
Rust

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[memsharded]

old triplet for iOS simulator was x86_64-apple-darwin (same as MacOS, which confused auto-tools configure scripts).
the new deduced triplet is x86_64-apple-ios.

But wouldn't this mean that if there are Conan users using the old iOS simulator we will break them?

[SSE4]

@memsharded nope, it won't break. basically, configure never ever passed for such old triplets, that's why recipes were using workarounds.

[SSE4]

for the record, the error was:

 > ./configure '--prefix=/Users/sse4/.conan/data/libiconv/1.16/_/_/package/6c12f63a312ce33f9e1610f0b8c55126373a1743' '--enable-static' '--disable-shared' '--bindir=${prefix}/bin' '--sbindir=${prefix}/bin' '--libexecdir=${prefix}/bin' '--libdir=${prefix}/lib' '--includedir=${prefix}/include' '--oldincludedir=${prefix}/include' '--datarootdir=${prefix}/share' --build=x86_64-apple-darwin --host=x86_64-apple-darwin
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... build-aux/install-sh -c -d
checking for gawk... no
checking for mawk... no
checking for nawk... no
checking for awk... awk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether make sets $(MAKE)... (cached) yes
checking for x86_64-apple-darwin-gcc... /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... configure: error: in `/Users/sse4/.conan/data/libiconv/1.16/_/_/build/6c12f63a312ce33f9e1610f0b8c55126373a1743/source_subfolder':
configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details

(NOTICE: --build=x86_64-apple-darwin --host=x86_64-apple-darwin)
and config.log has:

configure:4358: checking whether we are cross compiling
configure:4370: $? = 0
configure:4377: ./conftest
dyld: attempt to run simulator program outside simulator (DYLD_ROOT_PATH not set)
./configure: line 4379: 72890 Abort trap: 6           ./conftest$ac_cv_exeext
configure:4381: $? = 134
configure:4388: error: in `/Users/sse4/.conan/data/libiconv/1.16/_/_/build/6c12f63a312ce33f9e1610f0b8c55126373a1743/source_subfolder':
configure:4390: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.

after the fix, it has --build=x86_64-apple-darwin --host=x86_64-apple-ios
and configure finishes gracefully:

checking whether we are cross compiling... yes

[maikelvdh]

Is there a plan to get this change merged in? ping @memsharded

[memsharded]

Sorry about this, merged, will be in next 1.27