Backported upstream PR:

Updated to merged branches from git://gcc.gnu.org/git/gcc.git (fixes FTBFS
10-branch
10

Updated to merged branches from git://gcc.gnu.org/git/gcc.git (ALT#39798):
10-branch
10
gcc10-plugin-devel: added R: libgmp-devel.

Enabled hardenings by default:
Wl,-z,now for PIE executables.
Merged lto1 and lto-dump programs into one binary.

Updated to git://gcc.gnu.org/git/gcc.git vendors/redhat/heads/gcc-10-branch
Synced with Fedora gcc 10.2.1-9 and Debian gcc-10 10.2.0-18.

Updated to git://gcc.gnu.org/git/gcc.git releases/gcc-9
Rebased redhat vendor branch to releases/gcc-9 branch.

Updated to git://gcc.gnu.org/git/gcc.git vendors/redhat/heads/gcc-9-branch
Fixed License tag.

gdc: add R: gcc-gdc-common.

Updated to redhat/gcc-9-branch r274959.
Synced with Fedora gcc 9.2.1-1 and Debian gcc-9 9.2.1-9.

Applied upstream fix for PR 89906 (closes: #36972).
Removed versioning of lib{cc1,cc1plugin,cp1plugin} libraries

Updated to redhat/gcc-8-branch r270976 (Fedora gcc-8.3.1-4).

Upgraded default -fstack-protector to -fstack-protector-strong.
Fixed build with libtool 2.4.6.

Updated to redhat/gcc-8-branch r269592 (Fedora gcc-8.3.1-3).

Updated to redhat/gcc-8-branch r269162 (Fedora gcc-8.3.1-2).

Updated to redhat/gcc-8-branch r268720 (Fedora gcc-8.2.1-8).

Added ppc64le support (by glebfm@).
Fixed profiledbootstrap build (by glebfm@).
g++: enabled -Werror=return-type by default (closes: #36038).
libcc1.so.0: cleaned up using a fixed libtool (closes: #36045).