EDIT: Stable GCC 7.1.0 is already released - see first reply below for details!
If you're very impatient waiting for the full GCC 7.1.0 release (expected this month), you can try experimental GCC 7 version with your ARM microcontroller right now (;
$ arm-none-eabi-gcc --version arm-none-eabi-gcc (bleeding-edge-toolchain) 7.0.1 20170402 (experimental) Copyright (C) 2017 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
https://github.com/FreddieChopin/bleeding-edge-toolchain/tree/gcc-7-experimental
The script is able to produce a working toolchain for Linux. It is also possible to cross-compile a toolchain for Windows (32-bit or 64-bit) - either in Linux or in "Bash on Ubuntu on Windows" (I've heard it can be done, but the process is painfully slow - who would expect that? (; ).
I've tested that toolchain briefly and it appears to work fine (;
Yes, you are right - none of the configurations from the new "rmprofile" uses big-endian. But this is definitely something that can be added and in fact two previous version of bleeding-edge-toolchain (with gcc 6) had such configuration for ARMv7-R. This configuration was contributed on github, but since in gcc 7 things changed and the user which contributed that patch did not reply I had to remove this functionality... If anyone is interested, here is the commit that removes that patch github.com/.../c8911853738dd5e1fa0d833c317da3806a92464b If anyone will be able to port it to gcc 7 and maintain it we can integrate that again. Of course it would be best if ARM would push such big-endian support upstream - if there is a demand for something like that.
Generally the patch to add such big-endian support is not very hard to make, but I have absolutely no means to test such feature, so I do not think I am the right person to do that... Beside different location, the contents of the file is "reorganized", so the porting probably will not be trivial. In any case - if you face some problems, let me know, I cannot say that I fully understand the syntax of these files, but I have some knowledge about that, so maybe I will be able to help. You can also try contacting the person who submitted the original patch to bleeding-edge-toolchain.