EXIV2_ENABLE_SSH: Fix compatibility with >=libssh-0.9.2

0.9.1 remains broken regardless and is beyond fixing in this place.

Build-tested with both libssh 0.9.0 and 0.9.2.

Solution copied from KDE's kio-extras commit 24506c2af8d1904a99538543804306c6c2b81ca2

cmake/findDependencies.cmake

@@ -26,8 +26,17 @@ if( EXIV2_ENABLE_WEBREADY )
 
     if( EXIV2_ENABLE_SSH )
         find_package(libssh CONFIG REQUIRED)
-    endif( )
-endif( )
+        # Define an imported target to have compatibility with <=libssh-0.9.0
+        # libssh-0.9.1 is broken regardless.
+        if(NOT TARGET ssh)
+            add_library(ssh SHARED IMPORTED)
+            set_target_properties(ssh PROPERTIES
+                IMPORTED_LOCATION "${LIBSSH_LIBRARIES}"
+                INTERFACE_INCLUDE_DIRECTORIES "${LIBSSH_INCLUDE_DIR}"
+            )
+        endif()
+    endif()
+endif()
 
 if (EXIV2_ENABLE_XMP AND EXIV2_ENABLE_EXTERNAL_XMP)
     message(FATAL_ERROR "EXIV2_ENABLE_XMP AND EXIV2_ENABLE_EXTERNAL_XMP are mutually exclusive.  You can only choose one of them")

src/CMakeLists.txt

@@ -173,8 +173,7 @@ target_include_directories(exiv2lib_int PUBLIC
 if (EXIV2_ENABLE_WEBREADY)
 
     if( EXIV2_ENABLE_SSH )
-        target_include_directories(exiv2lib SYSTEM PUBLIC ${LIBSSH_INCLUDE_DIR})
-        target_link_libraries(exiv2lib PUBLIC ${LIBSSH_LIBRARIES})
+        target_link_libraries(exiv2lib PUBLIC ssh)
     endif()
 
     if( EXIV2_ENABLE_CURL )