musl: fix building gcc-go on risv64

srcpkgs/musl/patches/riscv64-ucontext.patch

@@ -0,0 +1,29 @@
+From 56f0631d9553dc06530ff661527cf1fcd595a0d1 Mon Sep 17 00:00:00 2001
+From: Drew DeVault <sir@cmpwn.com>
+Date: Sat, 5 Dec 2020 18:10:06 +0000
+Subject: [PATCH] riscv64: fix inconsistent ucontext_t struct tag
+
+ucontext.h depends on the internal struct tag name for namespacing
+reasons, and the intent was always for it to be consistent across
+archs anyway.
+---
+ arch/riscv64/bits/signal.h | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/arch/riscv64/bits/signal.h b/arch/riscv64/bits/signal.h
+index b006334f7..287367db7 100644
+--- a/arch/riscv64/bits/signal.h
++++ b/arch/riscv64/bits/signal.h
+@@ -60,10 +60,10 @@ struct sigaltstack {
+ 	size_t ss_size;
+ };
+ 
+-typedef struct ucontext_t
++typedef struct __ucontext
+ {
+ 	unsigned long uc_flags;
+-	struct ucontext_t *uc_link;
++	struct __ucontext *uc_link;
+ 	stack_t uc_stack;
+ 	sigset_t uc_sigmask;
+ 	mcontext_t uc_mcontext;