CMake: Do not compile/use included "getopt" if OS has native implemen…

…tation. (#163)

* Only compile getopt if no native implementation found.

CMakeLists.txt

@@ -83,7 +83,13 @@ set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 
 # Source groups
 
-file(GLOB SOURCE_FILES *.c)
+set(SOURCE_FILES
+    jpegoptim.c
+    jpegsrc.c
+    jpegdest.c
+    jpegmarker.c
+    misc.c
+    )
 source_group("Source Files" FILES ${SOURCE_FILES})
 
 
@@ -146,9 +152,9 @@ endif()
 
 # Include directories
 
-target_include_directories(${PROJECT_NAME} PUBLIC
-    "${CMAKE_CURRENT_SOURCE_DIR}"
-)
+#target_include_directories(${PROJECT_NAME} PUBLIC
+#    "${CMAKE_CURRENT_SOURCE_DIR}"
+#)
 
 
 # Compile definitions
@@ -280,6 +286,12 @@ target_compile_definitions(${PROJECT_NAME} PRIVATE
 )
 
 
+# Include getopt only if no native implementation found.
+if(NOT HAVE_GETOPT_LONG)
+    target_sources(${PROJECT_NAME} PRIVATE getopt.c getopt1.c)
+endif()
+
+
 # Attach a manifest file to support UTF-8 on compatible Windows systems (see https://learn.microsoft.com/en-us/windows/apps/design/globalizing/use-utf8-code-page)
 
 if(MSVC)