BUG: Ensure that EbsdLib targets macOS deployment version correctly

Signed-off-by: Michael Jackson <mike.jackson@bluequartz.net>

Author: imikejackson

CMakeLists.txt

@@ -103,14 +103,21 @@ set(EbsdLib_USE_GHC_FILESYSTEM OFF)
 if(APPLE)
   exec_program(uname ARGS -v  OUTPUT_VARIABLE DARWIN_VERSION)
   string(REGEX MATCH "[0-9]+" DARWIN_VERSION ${DARWIN_VERSION})
-  message(STATUS "DARWIN_VERSION ${DARWIN_VERSION}")
   if(DARWIN_VERSION VERSION_LESS 19)
     set(EbsdLib_USE_GHC_FILESYSTEM ON)
   endif()
-elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU" AND "${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+  if(CMAKE_OSX_DEPLOYMENT_TARGET VERSION_LESS 10.15)
+    set(EbsdLib_USE_GHC_FILESYSTEM ON)
+  endif()
+endif()
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" AND ${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
   set(EbsdLib_USE_GHC_FILESYSTEM ON)
 endif()
-message(STATUS "EbsdLib_USE_GHC_FILESYSTEM: ${EbsdLib_USE_GHC_FILESYSTEM}")
+
+message(STATUS "EbsdLib: DARWIN_VERSION ${DARWIN_VERSION}")
+message(STATUS "EbsdLib: CMAKE_OSX_DEPLOYMENT_TARGET: ${CMAKE_OSX_DEPLOYMENT_TARGET}")
+message(STATUS "EbsdLib: EbsdLib_USE_GHC_FILESYSTEM: ${EbsdLib_USE_GHC_FILESYSTEM}")
+
 if(EbsdLib_USE_GHC_FILESYSTEM)
   find_package(ghcFilesystem REQUIRED NAMES ghc_filesystem ghcFilesystem)
 endif()