[CMake] Add UR_USE_EXTERNAL_UMF to find pre-built UMF

For example, by configuring with `-Dumf_ROOT=/path/to/umf-install`.

Author: tcreech-intel

source/common/CMakeLists.txt

@@ -49,14 +49,22 @@ if (UR_STATIC_ADAPTER_L0)
     endif()
 endif()
 
-set(UMF_BUILD_TESTS OFF CACHE INTERNAL "Build UMF tests")
-set(UMF_BUILD_EXAMPLES OFF CACHE INTERNAL "Build UMF examples")
-set(UMF_BUILD_SHARED_LIBRARY ${UMF_BUILD_SHARED_LIBRARY} CACHE INTERNAL "Build UMF shared library")
-set(UMF_BUILD_LIBUMF_POOL_DISJOINT ON CACHE INTERNAL "Build Disjoint Pool")
-set(UMF_BUILD_CUDA_PROVIDER OFF CACHE INTERNAL "Build UMF CUDA provider")
-
-FetchContent_MakeAvailable(unified-memory-framework)
-FetchContent_GetProperties(unified-memory-framework)
+set(UR_USE_EXTERNAL_UMF "" CACHE BOOL "Use a pre-built UMF")
+
+if (UR_USE_EXTERNAL_UMF)
+  find_package(umf REQUIRED)
+  # Add an alias matching the FetchContent case
+  add_library(umf::headers ALIAS umf::umf_headers)
+else()
+  set(UMF_BUILD_TESTS OFF CACHE INTERNAL "Build UMF tests")
+  set(UMF_BUILD_EXAMPLES OFF CACHE INTERNAL "Build UMF examples")
+  set(UMF_BUILD_SHARED_LIBRARY ${UMF_BUILD_SHARED_LIBRARY} CACHE INTERNAL "Build UMF shared library")
+  set(UMF_BUILD_LIBUMF_POOL_DISJOINT ON CACHE INTERNAL "Build Disjoint Pool")
+  set(UMF_BUILD_CUDA_PROVIDER OFF CACHE INTERNAL "Build UMF CUDA provider")
+
+  FetchContent_MakeAvailable(unified-memory-framework)
+  FetchContent_GetProperties(unified-memory-framework)
+endif()
 
 if(UR_ENABLE_LATENCY_HISTOGRAM)
     set(HDR_HISTOGRAM_BUILD_STATIC CACHE INTERNAL ON "")