fix compilation with newer CMake

It seems CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS on CMake 3.27 breaks
compilation on Windows.

The reason for it here is wrong: unit tests do not need non exported
symbols.

CMakeLists.txt

@@ -79,10 +79,6 @@ if ( EXIV2_ENABLE_EXTERNAL_XMP )
   set(EXIV2_ENABLE_XMP OFF)
 endif()
 
-if(BUILD_TESTING AND EXIV2_BUILD_UNIT_TESTS)
-  set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON) # Requires CMake 3.3.3
-endif()
-
 include(cmake/findDependencies.cmake   REQUIRED)
 include(cmake/compilerFlags.cmake      REQUIRED)
 include(cmake/generateConfigFile.cmake REQUIRED)

src/CMakeLists.txt

@@ -1,9 +1,3 @@
-# Note that this is a hack for testing the internals of the library. If EXIV2_BUILD_UNIT_TESTS==OFF
-# Then we only export the symbols that are explicitly exported
-if(BUILD_TESTING AND EXIV2_BUILD_UNIT_TESTS)
-    set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON) # Requires CMake 3.3.3
-endif()
-
 include(CMakePackageConfigHelpers)
 
 include_directories(${CMAKE_CURRENT_BINARY_DIR})