Fix build error (riscv64 gofrontend)

Import a fix from upstream to allow go to build within GCC. This fix
should be removed once Jakub prepares GCC 10 0.8 release.

Signed-off-by: David Abdurachmanov <david.abdurachmanov@sifive.com>

79530f94e9c53153c4fae3b50a8c938f89db0c32.patch

@@ -0,0 +1,49 @@
+From 79530f94e9c53153c4fae3b50a8c938f89db0c32 Mon Sep 17 00:00:00 2001
+From: Ian Lance Taylor <iant@golang.org>
+Date: Mon, 3 Feb 2020 12:29:45 -0800
+Subject: [PATCH] syscall: fix riscv64 GNU/Linux build
+
+Make syscall_linux_riscv64.go, new in the 1.14beta1 release, look like
+the other syscall_linux_GOARCH.go files.
+
+Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/217577
+---
+ gcc/go/gofrontend/MERGE                   |  2 +-
+ libgo/go/syscall/syscall_linux_riscv64.go | 14 --------------
+ 2 files changed, 1 insertion(+), 15 deletions(-)
+
+diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
+index 40529518b264..27f4ce342e54 100644
+--- a/gcc/go/gofrontend/MERGE
++++ b/gcc/go/gofrontend/MERGE
+@@ -1,4 +1,4 @@
+-d796680b5a78f686ed118578e81d5b1adf48508d
++c94637ad6fd38d4814fb02d094a1a73f19323d71
+ 
+ The first line of this file holds the git revision number of the last
+ merge done from the gofrontend repository.
+diff --git a/libgo/go/syscall/syscall_linux_riscv64.go b/libgo/go/syscall/syscall_linux_riscv64.go
+index e9aab94e3a1f..16d8709708dc 100644
+--- a/libgo/go/syscall/syscall_linux_riscv64.go
++++ b/libgo/go/syscall/syscall_linux_riscv64.go
+@@ -4,20 +4,6 @@
+ 
+ package syscall
+ 
+-import "unsafe"
+-
+ func (r *PtraceRegs) PC() uint64 { return r.Pc }
+ 
+ func (r *PtraceRegs) SetPC(pc uint64) { r.Pc = pc }
+-
+-func (iov *Iovec) SetLen(length int) {
+-	iov.Len = uint64(length)
+-}
+-
+-func (msghdr *Msghdr) SetControllen(length int) {
+-	msghdr.Controllen = uint64(length)
+-}
+-
+-func (cmsg *Cmsghdr) SetLen(length int) {
+-	cmsg.Len = uint64(length)
+-}

gcc.spec

@@ -261,6 +261,9 @@ Patch10: gcc10-rh1574936.patch
 Patch11: gcc10-d-shared-libphobos.patch
 Patch12: gcc10-pr92765-workaround.patch
 
+# https://github.com/gcc-mirror/gcc/commit/79530f94e9c53153c4fae3b50a8c938f89db0c32
+Patch20: 79530f94e9c53153c4fae3b50a8c938f89db0c32.patch
+
 # On ARM EABI systems, we do want -gnueabi to be part of the
 # target triple.
 %ifnarch %{arm}
@@ -773,6 +776,8 @@ to NVidia PTX capable devices if available.
 %patch11 -p0 -b .d-shared-libphobos~
 %patch12 -p0 -b .pr92765-workaround~
 
+%patch20 -p1 -b .gofrontend-riscv64~
+
 echo 'Red Hat %{version}-%{gcc_release}' > gcc/DEV-PHASE
 
 cp -a libstdc++-v3/config/cpu/i{4,3}86/atomicity.h