Generate RPM specfile only when targeting Linux platform.

build/CMakeLists.txt

@@ -42,7 +42,9 @@ message("-- Package file name is ${CPACK_PACKAGE_FILE_NAME}" )
 
 set(CPACK_SOURCE_PACKAGE_FILE_NAME ${CPACK_PACKAGE_FILE_NAME})
 
-configure_file("rpm/bcg729.spec.cmake" "${PROJECT_SOURCE_DIR}/bcg729.spec" @ONLY)
+if(UNIX AND NOT APPLE AND NOT ANDROID)
+	configure_file("rpm/bcg729.spec.cmake" "${PROJECT_SOURCE_DIR}/bcg729.spec" @ONLY)
+endif()
 
 include(CPack)