mknative-gcc for GCC 10 and almost all platforms. one of the
myriad of arm platforms, and the powerpc* platforms are not
yet done.

regen mknative-gcc and GCC 7 for earm targets: use generic unwind

mknative-gcc for GCC 7 and earm targets.

generate mknative-gcc for GCC 5.3 and all the arm targets.
minor regen for x86 and sparc*

merge GCC 4.8 build.