fixup! [CMake] Make XROOTD target-based.

Author: hageboeck

cmake/modules/SearchInstalledSoftware.cmake

@@ -968,8 +968,8 @@ if(xrootd AND NOT builtin_xrootd)
     endif()
   else()
     set(XROOTD_VERSIONNUM ${xrdversnum})  # variable used internally
+    add_library(XROOTD ALIAS XROOTD::XROOTD)
   endif()
-  add_library(XROOTD ALIAS XROOTD::XROOTD)
 endif()
 
 if(builtin_xrootd AND NO_CONNECTION)
@@ -1000,7 +1000,7 @@ if(builtin_xrootd)
                        ${XROOTD_ROOTDIR}/${XROOTD_LIBDIR}/libXrdClient${CMAKE_SHARED_LIBRARY_SUFFIX}
                        ${XROOTD_ROOTDIR}/${XROOTD_LIBDIR}/libXrdCl${CMAKE_SHARED_LIBRARY_SUFFIX})
   ExternalProject_Add(
-    XROOTD
+    BUILTIN_XROOTD
     URL ${XROOTD_SRC_URI}
     URL_HASH SHA256=86d8e4bd7382fb3053002cf3d58b997623d1d26db93c8891080603827f01b4cd
     INSTALL_DIR ${XROOTD_ROOTDIR}
@@ -1038,11 +1038,13 @@ if(builtin_xrootd)
             CODE "xrootd_libs_change_rpath(${XROOTD_ROOTDIR}/${XROOTD_LIBDIR} ${CMAKE_INSTALL_FULL_LIBDIR})"
     )
   endif()
-  set(XROOTD_TARGET XROOTD)
+  # Unclear if this is still needed by external projects:
+  set(XROOTD_TARGET BUILTIN_XROOTD)
   set(xrootd ON CACHE BOOL "Enabled because builtin_xrootd requested (${xrootd_description})" FORCE)
 
   # Create a usable target:
   add_library(XROOTD INTERFACE)
+  add_dependencies(XROOTD BUILTIN_XROOTD)
   target_link_libraries(XROOTD INTERFACE ${XROOTD_LIBRARIES})
   target_include_directories(XROOTD INTERFACE ${XROOTD_INCLUDE_DIRS})
   target_compile_options(XROOTD INTERFACE ${XROOTD_CFLAGS})