How to completely ignore BUILD_INTERFACE libraries in installation?

Code
1

Through that, I link private libraries with BUILD_INTERFACE genexpr and they wouldn’t be in the exported targets, but the libraries’ linked libraries will be and unfortunately when we run the install rule they will be installed. And i don’t have access to those libraries’ code to change. How can I remove those targets from being installed?

For testing:

TestingExports.text

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(TestinExports CXX)

add_subdirectory(ThatThing)

file(WRITE main.cc "int main() { }")
add_executable(${PROJECT_NAME} main.cc)
target_link_libraries(${PROJECT_NAME} PRIVATE $<BUILD_INTERFACE:ThatThing>)

install(TARGETS ${PROJECT_NAME} EXPORT ${PROJECT_NAME}Config)
install(EXPORT ${PROJECT_NAME}Config DESTINATION lib/cmake)

ThatThing/CMakeLists.txt

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(ThatThing CXX)

add_subdirectory(ThoseLibraries)

file(WRITE that_thing.cc "void Function() { }")
add_library(${PROJECT_NAME} STATIC that_thing.cc)
target_link_libraries(${PROJECT_NAME} PRIVATE ThoseLibraries)

ThatThing/ThoseLibraries/CMakeLists.txt

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(ThoseLibraries CXX)

file(WRITE those_libraries.cc "void AnotherFunction() { }")
add_library(${PROJECT_NAME} STATIC those_libraries.cc)

install(TARGETS ${PROJECT_NAME} EXPORT ${PROJECT_NAME}Config)
install(EXPORT ${PROJECT_NAME}Config DESTINATION lib/cmake)

After we build and install we can see that ThoseLibraries is also installed:

$ cmake -B build -DCMAKE_INSTALL_PREFIX=$PWD/install
$ cmake --build build
$ cmake --install build
-- Install configuration: ""
-- Installing: /tmp/export_set/install/lib/libThoseLibraries.a
-- Installing: /tmp/export_set/install/lib/cmake/ThoseLibrariesConfig.cmake
-- Installing: /tmp/export_set/install/lib/cmake/ThoseLibrariesConfig-noconfig.cmake
-- Installing: /tmp/export_set/install/bin/TestinExports
-- Installing: /tmp/export_set/install/lib/cmake/TestinExportsConfig.cmake
-- Installing: /tmp/export_set/install/lib/cmake/TestinExportsConfig-noconfig.cmake
2

You’ll need to mask these install() commands somehow.

3

For me the most successful strategy has been to always use components for my install commands, then set CPack variables so that only my components would get installed.

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4

I handle this case by adding EXCLUDE_FROM_ALL to add_subdirectory().

add_subdirectory(ThoseLibraries EXCLUDE_FROM_ALL)
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