[PATCH] Fix build with latest GCC 9.0 tree

[Dimitar Dimitrov <dimitar@dinux.eu>]

A recent patch [1] to fix a GCC PR [2] actually broke the GDB build.
To fix, remove the stack pointer clobber. GCC will ignore the clobber
marker, and will not save or restore the stack pointer.

I ran "make check-gdb" on x86_64 to ensure there are no regressions.

gdb/ChangeLog:

2018-12-17  Dimitar Dimitrov  <dimitar@dinux.eu>

	* nat/linux-ptrace.c (linux_ptrace_test_ret_to_nx): Remove sp clobbers.

[1] https://gcc.gnu.org/ml/gcc-patches/2018-12/msg00532.html
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52813

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
---
 gdb/nat/linux-ptrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 1f21ef03a3..58aed199bf 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -128,14 +128,14 @@ linux_ptrace_test_ret_to_nx (void)
 			".globl linux_ptrace_test_ret_to_nx_instr;"
 			"linux_ptrace_test_ret_to_nx_instr:"
 			"ret"
-			: : "r" (return_address) : "%esp", "memory");
+			: : "r" (return_address) : "memory");
 #elif defined __x86_64__
 	  asm volatile ("pushq %0;"
 			".globl linux_ptrace_test_ret_to_nx_instr;"
 			"linux_ptrace_test_ret_to_nx_instr:"
 			"ret"
 			: : "r" ((uint64_t) (uintptr_t) return_address)
-			: "%rsp", "memory");
+			: "memory");
 #else
 # error "!__i386__ && !__x86_64__"
 #endif
-- 
2.11.0