I am currently migrating a couple of CodeBlock projects to use CMake and Visual Studio Code. I am facing an issue related to the include directory not being known by the consuming target.

I followed a guide so far as I was not aware of the "modern CMake way" using targets at all until yet. Mainly referring to here: https://rix0r.nl/blog/2015/08/13/cmake-guide/ and the official CMake docs.
There are two libraries (.so). One of them needs to other one to be there (build) when it get's loaded by the application later on.
I am not sure if everything is even intended to work like I assume it to work so I will just continue with the code and the expected result.

Library A (which is needed by Library B) has following CMakeLists

cmake_minimum_required(VERSION 3.0.0)
project(A)

set(SOURCE somesource.c)

include(GNUInstallDirs)

find_package(JNI REQUIRED)
add_library(JNI SHARED IMPORTED)
set_property(TARGET JNI PROPERTY INTERFACE_INCLUDE_DIRECTORIES $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux)
set_property(TARGET JNI PROPERTY IMPORTED_LOCATION $JNI_LIBRARIES)

add_library($PROJECT_NAME SHARED $SOURCE)

target_include_directories($PROJECT_NAME 
 PUBLIC 
 $<BUILD_INTERFACE:$CMAKE_CURRENT_SOURCE_DIR/include $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux>
 $<INSTALL_INTERFACE:include>
)

install(DIRECTORY include/ DESTINATION $CMAKE_INSTALL_INCLUDEDIR)

install(TARGETS $PROJECT_NAME EXPORT $PROJECT_NAMEConfig
 LIBRARY DESTINATION $CMAKE_INSTALL_LIBDIR)

install(EXPORT $PROJECT_NAMEConfig DESTINATION $CMAKE_INSTALL_PREFIX/cmake)

Notice I only have one include file which is public and located in "include", so its used by the library itself but should also be part of the install interface
used by the "consuming" target.

Library B (which uses Library A and its header)

cmake_minimum_required(VERSION 3.0)
project(B)

set(SOURCE somesource.c)

add_library($PROJECT_NAME SHARED $SOURCE)

find_package(A REQUIRED)

target_include_directories($PROJECT_NAME
 PRIVATE $PROJECT_SOURCE_DIR
)

So in Library B I assume that I do not need to add the include_directories from Library A again. This is why I actually did the target approach so there is no need to keep track of linker/include dependencies. "find_package" should handle these on it's own right? I do not link neither because it is a shared object, not a static library.
Both libraries use the same CMAKE_INSTALL_PREFIX ofc and library A has been installed (make install). I double-checked on this. In case of using a different prefix or not doing the install, CMake already complains about not finding it.

So considering the issue now:
Within a source file from library B, I am using

#include <libcobjava.h>

resulting in an error when building as the compiler complains about "No such file or directory" Am I missing something? The file is definitely located at
CMAKE_INSTALL_PREFIX/include.

Apart from that as I am still new to CMake: Is this even the way you would do things if you own all the source?

Edit: Some more details on the follow-up issue as discussed in comments. Library A is libcobjava.

First I had the target_include_directories part as following (including the path where jni.h is located in $<INSTALL_INTERFACE:)

target_include_directories($PROJECT_NAME 
 PUBLIC 
 $<BUILD_INTERFACE:$CMAKE_CURRENT_SOURCE_DIR/include $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux> 
 $<INSTALL_INTERFACE:include $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux> 
)

results in following error:

[cmake] Configuring done
[cmake] CMake Error in CMakeLists.txt:
[cmake] Target "libcobjava" INTERFACE_INCLUDE_DIRECTORIES property contains path:
[cmake] 
[cmake] "/media/rbs42/data/Gebos/RBS42/tools/libcobjava/$_IMPORT_PREFIX/include"
[cmake] 
[cmake] which is prefixed in the source directory.
[cmake] 
[cmake] 
[cmake] Generating done
[cms-driver] Error during CMake configure: [cmake-server] Failed to compute build system.

This is why I removed $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux> from $<INSTALL_INTERFACE again.

The actual error I am getting in library B now is during compiling:

[build] /media/rbs42/data/rbs42/usr/include/libcobjava.h:1:10: fatal error: jni.h: No such file or directory
[build] #include <jni.h>

because library B does not have the include directories from library A that are not included in the $<INSTALL_INTERFACE. This is what one would expect. And thats the reason I added the following code before in library A.

set_property(TARGET JNI PROPERTY INTERFACE_INCLUDE_DIRECTORIES $ENVJAVA_HOME/include $ENVJAVA_HOME/include/linux)

which I assumed is taking care of propagating the include dependencies from library A to the "consuming" library B, although they are not part of the $<INSTALL_INTERFACE.