update how version is checked in macOSX

Author: hp77-creator

cmake/darwin/default_libs.cmake

@@ -17,10 +17,12 @@ find_package(Threads REQUIRED)
 
 if(NOT CMAKE_CROSSCOMPILING)
     execute_process(
-        COMMAND xcrun --sdk macosx --show-sdk-version
-        OUTPUT_VARIABLE OS_DARWIN_SDK_VERSION
+        COMMAND readlink -f /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
+        OUTPUT_VARIABLE ACTUAL_SDK_PATH
         OUTPUT_STRIP_TRAILING_WHITESPACE
     )
+    string(REGEX MATCH "MacOSX([0-9]+\\.[0-9]+)" _ ${ACTUAL_SDK_PATH})
+    set(OS_DARWIN_SDK_VERSION ${CMAKE_MATCH_1})
     if(${OS_DARWIN_SDK_VERSION} MATCHES "^[0-9]+\\.[0-9]+")
         message(STATUS "Detected OSX SDK Version: ${OS_DARWIN_SDK_VERSION}")
     else ()