um: finish conversion to mcontext_t

now we don't mix host and guest signal frame layouts anymore; moreover,
we don't need host's struct sigcontext at all.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/arch/um/os-Linux/sys-x86/Makefile b/arch/um/os-Linux/sys-x86/Makefile
index 22cc507..253bfb8 100644
--- a/arch/um/os-Linux/sys-x86/Makefile
+++ b/arch/um/os-Linux/sys-x86/Makefile
@@ -3,7 +3,7 @@
 # Licensed under the GPL
 #
 
-obj-y = registers.o task_size.o
+obj-y = registers.o task_size.o mcontext.o
 
 obj-$(CONFIG_X86_32) += tls.o
 obj-$(CONFIG_64BIT) += prctl.o