[2.30 COMMITTED] Fix RISC-V vfork build with Linux 5.3 kernel headers.

[Aurelien Jarno <aurelien@aurel32.net>]

From: Joseph Myers <joseph@codesourcery.com>

Building glibc for RISC-V with Linux 5.3 kernel headers fails because
<linux/sched.h>, included in vfork.S for CLONE_* constants, contains a
structure definition not safe for inclusion in assembly code.

All other architectures already avoid use of that header in vfork.S,
either defining the CLONE_* constants locally or embedding the
required values directly in the relevant instruction, where they
implement vfork using the clone syscall (see the implementations for
aarch64, ia64, mips and nios2).  This patch makes the RISC-V version
define the constants locally like the other architectures.

Tested build for all three RISC-V configurations in
build-many-glibcs.py with Linux 5.3 headers.

	* sysdeps/unix/sysv/linux/riscv/vfork.S: Do not include
	<linux/sched.h>.
	(CLONE_VM): New macro.
	(CLONE_VFORK): Likewise.

(cherry picked from commit 8cacbcf4a984ccac24efedb795d9c8a7f149d17b)
---
 ChangeLog                             | 7 +++++++
 sysdeps/unix/sysv/linux/riscv/vfork.S | 5 ++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 3ea022b7387..29c864868ad 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2019-09-20  Joseph Myers  <joseph@codesourcery.com>
+
+	* sysdeps/unix/sysv/linux/riscv/vfork.S: Do not include
+	<linux/sched.h>.
+	(CLONE_VM): New macro.
+	(CLONE_VFORK): Likewise.
+
 2019-09-14  Aurelien Jarno  <aurelien@aurel32.net>
 
 	[BZ #24986]
diff --git a/sysdeps/unix/sysv/linux/riscv/vfork.S b/sysdeps/unix/sysv/linux/riscv/vfork.S
index 67373f181b2..dc173d6b47e 100644
--- a/sysdeps/unix/sysv/linux/riscv/vfork.S
+++ b/sysdeps/unix/sysv/linux/riscv/vfork.S
@@ -21,9 +21,12 @@
 #include <sys/asm.h>
 #include <sysdep.h>
 #define __ASSEMBLY__
-#include <linux/sched.h>
 #include <asm/signal.h>
 
+#define CLONE_VM      0x00000100 /* Set if VM shared between processes.  */
+#define CLONE_VFORK   0x00004000 /* Set if the parent wants the child to
+				    wake it up on mm_release.  */
+
 	.text
 LEAF (__libc_vfork)
 
-- 
2.23.0