[LLVM-571] Build GNU rmprofile toolchain with Linaro scripts (abe) The existing build-system was only set up to build the A-profile bare metal toolchain. Managed to find right combination of flags and modifications to get a toolchain that zephyr can use. [LLVM-158] Buildbot maintenance An interesting failure introduced in LLD, but causing segfaults in 2-stage build, now fixed. [LLVM-542] Zephyr code size investigation - Rebased modifications to Zephyr - Wrote script to build all the examples with GCC and Clang - Fixed problems with modifications found by building all the examples - Clang built helloworld no longer booting, need to investigate - Found some areas for more investigation: -- llvm-objcopy missing --gap-fill (used by one of the sample programs) -- lld missing --print-memory-usage, while I'm using gcc for the main link, zephyr build system seems to be feature testing using clang bare metal default linker (lld) -- clang always generates .note.GNU.stack, gcc embedded does not, leading to lots of orphan section warnings. Probably best solved by linker script modification.