fs: Handle case where old FD == new FD in fs_dup2()
fs: Remove unneeded include
kos-chain: Also copy <sys/lock.h> to arch-independent Newlib dir
Change GCCVER < 9 warning to GCCVER < 8
kos-chain: Build Newlib 4.6.0 for ARM7DI
kos-chain: Update GCC-8.5.0 patch to support ARM7DI
init: Don't export symbols by default
Move arch_exec functions to DC-specific exports