fix: set system definition in package file

PackageConfig.cmake.in

@@ -26,3 +26,24 @@ if(NOT ("@IMPLIB@" STREQUAL ""))
     set_property(TARGET __zenohpico_lib PROPERTY IMPORTED_IMPLIB "@CMAKE_INSTALL_PREFIX@/@CMAKE_INSTALL_LIBDIR@/@IMPLIB@")
 endif()
 target_include_directories(__zenohpico_lib INTERFACE "@CMAKE_INSTALL_PREFIX@/@CMAKE_INSTALL_INCLUDEDIR@")
+
+if(CMAKE_SYSTEM_NAME MATCHES "Linux")
+  add_compile_definitions(ZENOH_LINUX)
+elseif(POSIX_COMPATIBLE)
+  add_compile_definitions(ZENOH_LINUX)
+elseif(CMAKE_SYSTEM_NAME MATCHES "BSD")
+  add_compile_definitions(ZENOH_BSD)
+elseif(CMAKE_SYSTEM_NAME MATCHES "Darwin")
+  add_compile_definitions(ZENOH_MACOS)
+elseif(CMAKE_SYSTEM_NAME MATCHES "Emscripten")
+  add_compile_definitions(EMSCRIPTEN)
+elseif(CMAKE_SYSTEM_NAME MATCHES "Windows")
+  add_compile_definitions(ZENOH_WINDOWS)
+elseif(CMAKE_SYSTEM_NAME MATCHES "Generic")
+  if(WITH_ZEPHYR)
+    add_compile_definitions(ZENOH_ZEPHYR)
+  elseif(WITH_FREERTOS_PLUS_TCP)
+    add_compile_definitions(ZENOH_FREERTOS_PLUS_TCP)
+  endif()
+endif()
+

examples/CMakeLists.txt

@@ -19,7 +19,6 @@ function(add_example name)
 endfunction()
 
 if(UNIX)
-    add_definitions(-DZENOH_LINUX)
     if(CMAKE_C_STANDARD MATCHES "99")
         add_example(z_put unix/c99/z_put.c)
         add_example(z_pub unix/c99/z_pub.c)
@@ -50,7 +49,6 @@ if(UNIX)
         add_example(z_sub_thr unix/c11/z_sub_thr.c)
     endif()
 elseif(MSVC)
-    add_definitions(-DZENOH_WINDOWS)
     add_example(z_put windows/z_put.c)
     add_example(z_pub windows/z_pub.c)
     add_example(z_pub_st windows/z_pub_st.c)