CMake: expose *_STATIC_PLUGINS options only if they make sense.

I.e., if the build is static including plugins and the corresponding
application is actually enabled. The options will work even if not
(because it's easier that way), they will just not appear in the CMake
option list.

CMakeLists.txt

@@ -156,20 +156,31 @@ endif()
 # option everywhere for simplicity.
 if(CORRADE_TARGET_UNIX OR CORRADE_TARGET_WINDOWS)
     option(MAGNUM_WITH_FONTCONVERTER "Build magnum-fontconverter utility" OFF)
-    option(MAGNUM_WITH_DISTANCEFIELDCONVERTER "Build magnum-distancefieldconverter utility" OFF)
-
+    if(MAGNUM_WITH_FONTCONVERTER AND MAGNUM_BUILD_STATIC AND MAGNUM_BUILD_PLUGINS_STATIC)
         set(MAGNUM_FONTCONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-fontconverter utility")
+    endif()
+
+    option(MAGNUM_WITH_DISTANCEFIELDCONVERTER "Build magnum-distancefieldconverter utility" OFF)
+    if(MAGNUM_WITH_DISTANCEFIELDCONVERTER AND MAGNUM_BUILD_STATIC AND MAGNUM_BUILD_PLUGINS_STATIC)
         set(MAGNUM_DISTANCEFIELDCONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-distancefieldconverter utility")
+    endif()
 endif()
 
 # API-independent utilities
 option(MAGNUM_WITH_IMAGECONVERTER "Build magnum-imageconverter utility" OFF)
+if(MAGNUM_WITH_IMAGECONVERTER AND MAGNUM_BUILD_STATIC AND MAGNUM_BUILD_PLUGINS_STATIC)
+    set(MAGNUM_IMAGECONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-imageconverter utility")
+endif()
+
 option(MAGNUM_WITH_SCENECONVERTER "Build magnum-sceneconverter utility" OFF)
-option(MAGNUM_WITH_SHADERCONVERTER "Build magnum-shaderconverter utility" OFF)
+if(MAGNUM_WITH_SCENECONVERTER AND MAGNUM_BUILD_STATIC AND MAGNUM_BUILD_PLUGINS_STATIC)
+    set(MAGNUM_SCENECONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-sceneconverter utility")
+endif()
 
-set(MAGNUM_IMAGECONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-imageconverter utility")
-set(MAGNUM_SCENECONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-sceneconverter utility")
-set(MAGNUM_SHADERCONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-shaderconverter utility")
+option(MAGNUM_WITH_SHADERCONVERTER "Build magnum-shaderconverter utility" OFF)
+if(MAGNUM_WITH_SHADERCONVERTER AND MAGNUM_BUILD_STATIC AND MAGNUM_BUILD_PLUGINS_STATIC)
+    set(MAGNUM_SHADERCONVERTER_STATIC_PLUGINS "" CACHE STRING "Static plugins to link to the magnum-shaderconverter utility")
+endif()
 
 # Magnum AL Info
 option(MAGNUM_WITH_AL_INFO "Build magnum-al-info utility" OFF)