CMake/macOS: Use custom LIBDIR if set on CLI

Reviewed By: ankitm
Maniphest Tasks: T83174
Differential Revision: https://developer.blender.org/D9664

build_files/cmake/platform/platform_apple.cmake

@@ -73,9 +73,6 @@ endif()
 
 if(NOT DEFINED LIBDIR)
   set(LIBDIR ${CMAKE_SOURCE_DIR}/../lib/darwin)
-  # Prefer lib directory paths
-  file(GLOB LIB_SUBDIRS ${LIBDIR}/*)
-  set(CMAKE_PREFIX_PATH ${LIB_SUBDIRS})
 else()
   message(STATUS "Using pre-compiled LIBDIR: ${LIBDIR}")
 endif()
@@ -83,6 +80,10 @@ if(NOT EXISTS "${LIBDIR}/")
   message(FATAL_ERROR "Mac OSX requires pre-compiled libs at: '${LIBDIR}'")
 endif()
 
+# Prefer lib directory paths
+file(GLOB LIB_SUBDIRS ${LIBDIR}/*)
+set(CMAKE_PREFIX_PATH ${LIB_SUBDIRS})
+
 # -------------------------------------------------------------------------
 # Find precompiled libraries, and avoid system or user-installed ones.