update arm64ec default flags and lib
add softintrin.lib to CMAKE_C_STANDARD_LIBRARIES_INIT for arm64ec. remove /D_ARM64EC_WORKAROUND from the flags for arm64ec as no longer needed.
add softintrin.lib to CMAKE_C_STANDARD_LIBRARIES_INIT for arm64ec. remove /D_ARM64EC_WORKAROUND from the flags for arm64ec as no longer needed.