README.md: Added experimental flag & updated gccrs path

[MahadMuhammad]

(1) There is a need of the flag "-frust-incomplete-and-experimental-compiler-do-not-use" because the rust1 compiler didn't work without this.

(2) The gccrs was not present in the $HOME/gccrs-install/, so updated the path to $HOME/gccrs-install/bin

Signed-off-by: MAHAD mahadtxt@gmail.com

[CohenArthur]

Thank you for the pull request! And good catch :)

[CohenArthur]

I think the README deserves some more love as it's probably a bit out of date. I'll merge this for now, and have a look at how to improve it very soon.

bors r+

[tschwinge]

I had considered to raise the need to update README.md for -frust-incomplete-and-experimental-compiler-do-not-use in its PR #1540 "Implement -frust-incomplete-and-experimental-compiler-do-not-use flag", but then decided to not do so -- in order to not cut new contributors/users out of that first-hand experience. ;-) (But of course I don't object to updating the file, either.)

[bors]

Build succeeded:

• build-and-check-gcc-48
• build-and-check-ubuntu-32bit
• build-and-check-ubuntu-64bit

[CohenArthur]

I had considered to raise the need to update README.md for -frust-incomplete-and-experimental-compiler-do-not-use in its PR #1540 "Implement -frust-incomplete-and-experimental-compiler-do-not-use flag", but then decided to not do so -- in order to not cut new contributors/users out of that first-hand experience. ;-) (But of course I don't object to updating the file, either.)

Yes, that's what I was thinking yesterday as well :) I don't know how to feel about it. I think it's worth mentioning the flag in more detail in the README which will solve that issue.