Merge changes I92ddea0b,Ice8474ae,If63cc6ce,I1d6f1388,Ic3da07c8, ...

* changes:
  Add Mega_device configuration option
  Toolchain modules use GCC
  Apply ToolchainLdflags to clang builds
  Add Clang Asflags for mips
  Remove libgcov for now to fix X86 devices
  Change clang extra flags behavior