[SYCL][CMake] Don't try to install UMF if using external UMF (#18968)

If we're using the system preinstalled one, don't try to install it.

Manually tested this.

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

Author: sarnex

sycl/cmake/modules/FetchUnifiedRuntime.cmake

@@ -425,7 +425,9 @@ if(CMAKE_SYSTEM_NAME STREQUAL Windows)
   endif()
 endif()
 
-install(TARGETS umf
-  LIBRARY DESTINATION "lib${LLVM_LIBDIR_SUFFIX}" COMPONENT unified-memory-framework
-  ARCHIVE DESTINATION "lib${LLVM_LIBDIR_SUFFIX}" COMPONENT unified-memory-framework
-  RUNTIME DESTINATION "bin" COMPONENT unified-memory-framework)
+if(NOT UR_USE_EXTERNAL_UMF)
+  install(TARGETS umf
+    LIBRARY DESTINATION "lib${LLVM_LIBDIR_SUFFIX}" COMPONENT unified-memory-framework
+    ARCHIVE DESTINATION "lib${LLVM_LIBDIR_SUFFIX}" COMPONENT unified-memory-framework
+    RUNTIME DESTINATION "bin" COMPONENT unified-memory-framework)
+endif()