CGAL_Setup${cgal_lib}CoreDependencies improve

- Now even CGAL_Core has one.
- The `${cgal_lib}_FOUND` are now set in those modules, after having chec
- For self-consistency, `Use_CGAL_Qt5_headers` is included by
  `CGAL_SetupCGAL_Qt5Dependencies`.

CGAL_Core/src/CGAL_Core/CMakeLists.txt

@@ -1,14 +1,18 @@
+include(CGAL_SetupCGAL_CoreDependencies)
+
 message("Configuring libCGAL_Core")
+if(CGAL_Core_FOUND)
 
-collect_cgal_library(CGAL_Core "")
+  collect_cgal_library(CGAL_Core "")
 
-if(CGAL_HEADER_ONLY)
-  set(keyword INTERFACE)
-else()
-  set(keyword PUBLIC)
+  if(CGAL_HEADER_ONLY)
+    set(keyword INTERFACE)
+  else()
+    set(keyword PUBLIC)
+  endif()
+
+  target_link_libraries( CGAL_Core ${keyword} CGAL::CGAL )
+
+  message("libCGAL_Core is configured")
 endif()
 
-target_link_libraries( CGAL_Core ${keyword} CGAL::CGAL )
-
-message("libCGAL_Core is configured")
-

Installation/cmake/modules/CGAL_SetupCGALDependencies.cmake

@@ -13,6 +13,10 @@ endif()
 
 include(CGAL_SetupBoost)
 
+if(Boost_FOUND)
+  set(CGAL_FOUND TRUE)
+endif()
+
 function(CGAL_setup_CGAL_dependencies target)
   if(ARGV1 STREQUAL INTERFACE)
     set(keyword INTERFACE)

Installation/cmake/modules/CGAL_SetupCGAL_CoreDependencies.cmake

@@ -0,0 +1,21 @@
+if(CGAL_SetupCGAL_CoreDependencies_included)
+  return()
+endif()
+set(CGAL_SetupCGAL_CoreDependencies_included TRUE)
+
+if(NOT CGAL_DISABLE_GMP)
+  include(CGAL_SetupGMP)
+  if(GMP_FOUND)
+    set(CGAL_Core_FOUND TRUE)
+  endif()
+endif()
+
+function(CGAL_setup_CGAL_Core_dependencies target)
+  if(ARGV1 STREQUAL INTERFACE)
+    set(keyword INTERFACE)
+  else()
+    set(keyword PUBLIC)
+  endif()
+  use_CGAL_GMP_support(CGAL_Core ${keyword})
+  target_link_libraries( CGAL_Core ${keyword} CGAL::CGAL )
+endfunction()

Installation/cmake/modules/CGAL_SetupCGAL_ImageIODependencies.cmake

@@ -15,9 +15,7 @@ endif(ZLIB_FOUND)
 
 set( CGAL_ImageIO_BASENAME CGAL_ImageIO)
 
-if(CGAL_HEADER_ONLY)
-  set(keyword "INTERFACE")
-endif()
+set(CGAL_ImageIO_FOUND TRUE)
 
 function(CGAL_setup_CGAL_ImageIO_dependencies target)
   if(ARGV1 STREQUAL INTERFACE)

Installation/cmake/modules/CGAL_SetupCGAL_Qt5Dependencies.cmake

@@ -20,6 +20,10 @@ if(NOT OPENGL_FOUND)
   set(CGAL_Qt5_MISSING_DEPS "${CGAL_Qt5_MISSING_DEPS} OpenGL")
 endif()
 
+if(NOT CGAL_Qt5_MISSING_DEPS)
+  set(CGAL_Qt5_FOUND TRUE)
+endif()
+
 get_property(QT_UIC_EXECUTABLE TARGET Qt5::uic PROPERTY LOCATION)
 message( STATUS "OpenGL include:      ${OPENGL_INCLUDE_DIR}" )
 message( STATUS "OpenGL libraries:    ${OPENGL_LIBRARIES}" )
@@ -44,3 +48,5 @@ function(CGAL_setup_CGAL_Qt5_dependencies target)
   target_link_libraries( ${target} ${keyword} CGAL::CGAL)
   target_link_libraries( ${target} ${keyword} Qt5::OpenGL Qt5::Svg ${OPENGL_LIBRARIES})
 endfunction()
+
+include(Use_CGAL_Qt5_headers)

Installation/cmake/modules/Use_CGAL_Qt5_headers.cmake

@@ -1,3 +1,7 @@
+if(NOT CGAL_Qt5_FOUND)
+  return()
+endif()
+
 if(Use_CGAL_Qt5_headers_included)
   return()
 endif()