Add opus and zlib source directoies as include directories only on Windows

external/opus/CMakeLists.txt

@@ -16,14 +16,12 @@ else()
     add_library(external_opus STATIC IMPORTED GLOBAL)
     add_library(desktop-app::external_opus ALIAS external_opus)
 
-    target_include_directories(external_opus SYSTEM
-    INTERFACE
-        ${libs_loc}/opus/include
-    )
-
     if (WIN32)
+        target_include_directories(external_opus
+        INTERFACE
+            ${libs_loc}/opus/include
+        )
         set(opus_lib_loc ${libs_loc}/opus/win32/VS2015/Win32)
-
         set_target_properties(external_opus PROPERTIES
             IMPORTED_LOCATION "${opus_lib_loc}/Release/opus.lib"
             IMPORTED_LOCATION_DEBUG "${opus_lib_loc}/Debug/opus.lib"

external/zlib/CMakeLists.txt

@@ -7,21 +7,13 @@
 add_library(external_zlib INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_zlib ALIAS external_zlib)
 
-if (NOT DESKTOP_APP_USE_PACKAGED AND NOT LINUX)
-    target_include_directories(external_zlib SYSTEM
-    INTERFACE
-        ${libs_loc}/zlib
-    )
-endif()
-
 if (DESKTOP_APP_USE_PACKAGED)
     find_package(ZLIB REQUIRED)
     target_link_libraries(external_zlib INTERFACE ZLIB::ZLIB)
 elseif (WIN32)
     target_compile_definitions(external_zlib INTERFACE ZLIB_WINAPI)
-
+    target_include_directories(external_zlib INTERFACE ${libs_loc}/zlib)
     set(zlib_lib_loc ${libs_loc}/zlib/contrib/vstudio/vc14/x86/ZlibStat$<IF:$<CONFIG:Debug>,Debug,ReleaseWithoutAsm>)
-
     target_link_libraries(external_zlib INTERFACE ${zlib_lib_loc}/zlibstat.lib)
 elseif (APPLE AND NOT build_osx)
     target_link_libraries(external_zlib INTERFACE /usr/local/macos/lib/libz.a)