Also extend our integration test double inclusion. It will still not
catch this case, because that requires
`cmake_minimum_required(VERSION 3.18)` or higher.
Fixes:
```
CMake Error at .../lib/cmake/libssh2/libssh2-config.cmake:8 (add_library):
add_library cannot create ALIAS target "libssh2::libssh2" because another
target with the same name already exists.
Call Stack (most recent call first):
CMakeLists.txt:24 (find_package)
CMake Error at .../lib/cmake/libssh2/libssh2-config.cmake:13 (add_library):
add_library cannot create ALIAS target "Libssh2::libssh2" because another
target with the same name already exists.
Call Stack (most recent call first):
CMakeLists.txt:24 (find_package)
```
Test to reproduce:
```cmake
cmake_minimum_required(VERSION 3.18) # must be 3.18 or higher
project(test)
find_package(libssh2 CONFIG)
find_package(libssh2 CONFIG) # fails
add_executable(test main.c)
target_link_libraries(test libssh2::libssh2)
```
Ref: https://cmake.org/cmake/help/latest/release/3.18.html#other-changes
Ref: https://cmake.org/cmake/help/v3.18/policy/CMP0107.html
Assisted-by: Kai Pastor
Assisted-by: Harry Mallon
Ref: https://github.com/curl/curl/pull/11913Closes#1216
- add `libssh2:libssh2` target that selects the shared lib if built,
otherwise the static one.
- re-add `Libssh2:libssh2` target for compatibility with v1.10.0 and
earlier. This is an alias for `libssh2:libssh2`.
- keep `libssh2:libssh2_shared` and `libssh2_libssh2_static` targets.
- allow using `find_package(libssh2)` in dependents as an alternative
to `find_package(Libssh2)`.
Co-authored-by: Radek Brich
Suggested-by: Haowei Hsu
Fixes#1103Fixes#731Closes#1104
