CMake: SwiftCore: Directory Swift Modules

[etcwilde]

The catalyst support in the driver requires that the swiftmodules for the catalyst slice live in the swiftmodule directory. CMake currently doesn't do this natively so this patch works around it by specifying the module path explicitly. The use of an empty custom command is used to hook up the dependency graph on the specific target swiftmodule files correctly.

This is only needed for catalyst builds that this time so limit the affect of this change to instances where we are building zippered catalyst binaries.

The nested structure also greatly simplifies the installation story. We simply need to copy the entire swiftmodule directory into the install location.

I'm not enabling this always since it's not clear to me that the dependency edge on the actual binary swiftmodule file is being created consistently. This is fine for clean builds since the swiftmodule directory and swiftmodule file are created in the same invocation, but might break dependency tracking in incremental builds.

This is a workaround until we can use CMP0195 --https://gitlab.kitware.com/cmake/cmake/-/merge_requests/10664

[etcwilde]

@swift-ci please smoke test

[compnerd]

Should we consider removing this? The standard library build does emit the textual interface for all targets and the work that Alexis is doing to always use the textual interface.

[compnerd]

Should we rework this as:

Suggested change

	if(SwiftCore_VARIANT_MODULE_TRIPLE)
	target_compile_options(${target} PRIVATE
	$<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_MODULE_TRIPLE}.swiftinterface>
	$<$<COMPILE_LANGUAGE:Swift>:-emit-private-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_MODULE_TRIPLE}.private.swiftinterface>
	"$<$<COMPILE_LANGUAGE:Swift>:SHELL:-emit-variant-module-interface-path ${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_VARIANT_MODULE_TRIPLE}.swiftinterface>"
	"$<$<COMPILE_LANGUAGE:Swift>:SHELL:-emit-variant-private-module-interface-path ${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_VARIANT_MODULE_TRIPLE}.private.swiftinterface>")
	else()
	target_compile_options(${target} PRIVATE
	$<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:${target},Swift_MODULE_NAME>.swiftinterface>
	$<$<COMPILE_LANGUAGE:Swift>:-emit-private-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:${target},Swift_MODULE_NAME>.private.swiftinterface>)
	endif()
	target_compile_options(${target} PRIVATE
	$<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:${target},Swift_MODULE_NAME>.swiftinterface>
	$<$<COMPILE_LANGUAGE:Swift>:-emit-private-module-interface-path$<SEMICOLON>${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:${target},Swift_MODULE_NAME>.private.swiftinterface>)
	if(SwiftCore_VARIANT_MODULE_TRIPLE)
	target_compile_options(${target] PRIVATE
	"$<$<COMPILE_LANGUAGE:Swift>:SHELL:-emit-variant-module-interface-path ${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_VARIANT_MODULE_TRIPLE}.swiftinterface>"
	"$<$<COMPILE_LANGUAGE:Swift>:SHELL:-emit-variant-private-module-interface-path ${CMAKE_CURRENT_BINARY_DIR}/${module_name}.swiftmodule/${SwiftCore_VARIANT_MODULE_TRIPLE}.private.swiftinterface>")
	endif()

[compnerd]

This does make some complexity. We already have to have the custom handling here, why not consider doing this unconditionally and always generating the thick module layout?

[etcwilde]

#82571 merged. Closing this PR.