This is more of a cosmetic change and a reminder that the CMake script hardcodes -O2. Source: https://github.com/ARMmbed/mbedtls/blob/mbedtls-2.7/CMakeLists.txt#L73 https://github.com/ARMmbed/mbedtls/blob/master/CMakeLists.txt#L97 Remove the release type option as it's already provided by the toolchain. Source: https://github.com/openwrt/openwrt/blob/master/include/cmake.mk#L50 Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>