[interactiveterminal] Make optional if requirements not met

This is orthogonal to the SKIP_* mechanism already documented
for avoiding modules. If the module is enabled, but its dependencies
are not present, don't bother building the module. This follows
e.g. plasmalnf as an "avoidably heavy dependency".

Related to a misplaced comment in ISSUE #956

src/modules/interactiveterminal/CMakeLists.txt

@@ -1,18 +1,20 @@
 find_package(ECM ${ECM_VERSION} REQUIRED NO_MODULE)
 
-include(KDEInstallDirs)
-include(GenerateExportHeader)
-
-find_package( KF5 REQUIRED Service Parts )
-
-include_directories( ${PROJECT_BINARY_DIR}/src/libcalamaresui
-                     ${QTERMWIDGET_INCLUDE_DIR} )
-
-set( CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
-                       ${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules )
+set( kf5_ver 5.41 )
 
+find_package( KF5Service ${kf5_ver} )
+find_package( KF5Parts ${kf5_ver} )
+set_package_properties(
+    KF5Service PROPERTIES
+    PURPOSE "For finding KDE services at runtime"
+)
+set_package_properties(
+    KF5Parts PROPERTIES
+    PURPOSE "For finding KDE parts at runtime"
+)
 
-calamares_add_plugin( interactiveterminal
+if ( KF5Parts_FOUND AND KF5Service_FOUND )
+    calamares_add_plugin( interactiveterminal
         TYPE viewmodule
         EXPORT_MACRO PLUGINDLLEXPORT_PRO
         SOURCES
@@ -24,4 +26,7 @@ calamares_add_plugin( interactiveterminal
             KF5::Service
             KF5::Parts
         SHARED_LIB
-)
+    )
+else()
+    calamares_skip_module( "interactiveterminal (missing requirements)" )
+endif()