CMake: Add a check whether QALCULATE_LIBRARIES works

without need to explicitly add CLN_LIBRARIES.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit e926ed5b1b)

ConfigureChecks.cmake

@@ -37,3 +37,26 @@ pkg_search_module( QALCULATE libqalculate )
 if( NOT QALCULATE_FOUND )
    tde_message_fatal( "libqalculate is required but was not found on your system." )
 endif( NOT QALCULATE_FOUND )
+
+
+##### check if libqalculate requires explicitly link libcln
+
+tde_save( CMAKE_REQUIRED_INCLUDES CMAKE_REQUIRED_LIBRARIES )
+set( CMAKE_REQUIRED_INCLUDES ${QALCULATE_INCLUDE_DIRS} )
+set( CMAKE_REQUIRED_LIBRARIES ${QALCULATE_LIBRARIES} )
+
+check_cxx_source_compiles("
+	#include <libqalculate/qalculate.h>
+	int main(int argc, char **argv) { Number n; return 0; } "
+	QALCULATE_LIBRARIES_WORKS
+)
+if( NOT QALCULATE_LIBRARIES_WORKS )
+  pkg_search_module( CLN cln )
+  if( NOT CLN_FOUND )
+     tde_message_fatal( "libqalculate require CLN library but it was not found on your system." )
+  endif( NOT CLN_FOUND )
+  list( APPEND QALCULATE_LIBRARIES ${CLN_LIBRARIES} )
+  message( STATUS "Added CLN_LIBRARIES to QALCULATE_LIBRARIES" )
+endif( )
+
+tde_restore( CMAKE_REQUIRED_INCLUDES CMAKE_REQUIRED_LIBRARIES )