build: Fix loader test building without std filesystem

Author: rpavlik

src/tests/loader_test/CMakeLists.txt

@@ -42,6 +42,9 @@ if(VulkanHeaders_FOUND)
     )
 endif()
 
+if(BUILD_WITHOUT_STD_FILESYSTEM)
+    target_compile_definitions(loader_test PRIVATE DISABLE_STD_FILESYSTEM)
+endif()
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
     if(MSVC)
         target_compile_definitions(loader_test PRIVATE _CRT_SECURE_NO_WARNINGS)
@@ -53,7 +56,10 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
         loader_test PRIVATE -Wall -Wno-unused-function -Wno-format-truncation
     )
 
-    target_link_libraries(loader_test -lstdc++fs openxr_loader m -lpthread)
+    target_link_libraries(loader_test openxr_loader m -lpthread)
+    if(NOT BUILD_WITHOUT_STD_FILESYSTEM)
+        target_link_libraries(loader_test stdc++fs)
+    endif()
 else()
     message(FATAL_ERROR "Unsupported Platform")
 endif()