Guard against adding to cache variable twice

Author: bandoti

ggml/CMakeLists.txt

@@ -278,9 +278,8 @@ execute_process(COMMAND ${GIT_EXE} rev-list --count HEAD
     OUTPUT_STRIP_TRAILING_WHITESPACE
 )
 
-if(${GGML_BUILD_NUMBER} EQUAL 1)
-    message(WARNING
-        "GGML build version fixed at 1 likely due to a shallow clone.")
+if(GGML_BUILD_NUMBER EQUAL 1)
+    message(WARNING "GGML build version fixed at 1 likely due to a shallow clone.")
 endif()
 
 execute_process(COMMAND ${GIT_EXE} rev-parse --short HEAD

ggml/src/CMakeLists.txt

@@ -252,10 +252,14 @@ function(ggml_add_backend_library backend)
     endif()
 
     if(NOT GGML_AVAILABLE_BACKENDS)
-        set(GGML_AVAILABLE_BACKENDS "${backend}" CACHE INTERNAL "List of backends for cmake package")
-    else()
-        set(GGML_AVAILABLE_BACKENDS "${GGML_AVAILABLE_BACKENDS};${backend}"
+        set(GGML_AVAILABLE_BACKENDS "${backend}"
             CACHE INTERNAL "List of backends for cmake package")
+    else()
+        list(FIND GGML_AVAILABLE_BACKENDS "${backend}" has_backend)
+        if(has_backend EQUAL -1)
+            set(GGML_AVAILABLE_BACKENDS "${GGML_AVAILABLE_BACKENDS};${backend}"
+                CACHE INTERNAL "List of backends for cmake package")
+        endif()
     endif()
 endfunction()