Merge branch 'RPMHandlingFix-1.0.27-patches-20201007' into '1.0.27-patches'

RPM Handling Fix, 1.0.27-patches branch (2020.10.07.)

See merge request !753

Build/AtlasLCG/modules/LCGFunctions.cmake

@@ -185,6 +185,14 @@ function( lcg_need_rpm name )
       return()
    endif()
 
+   # If an LCG release *is* set up, but it doesn't provide this external,
+   # then stop as well.
+   string( TOUPPER ${name} nameUpper )
+   if( NOT ${name}_ROOT AND NOT ${nameUpper}_ROOT )
+      return()
+   endif()
+   unset( nameUpper )
+
    # Create the "found name" of the package:
    if( ARG_FOUND_NAME )
       set( nameFound ${ARG_FOUND_NAME} )