ntdll: Include ucontext.h on ARM64 for Android

[André Hentschel]

Yes, this is the first Android 64-bit related patch, NDK r10 supports
64-bit architectures

---
 dlls/ntdll/signal_arm64.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/dlls/ntdll/signal_arm64.c b/dlls/ntdll/signal_arm64.c
index 2b82952..fc6ce0b 100644
--- a/dlls/ntdll/signal_arm64.c
+++ b/dlls/ntdll/signal_arm64.c
@@ -28,6 +28,11 @@
 #include <stdlib.h>
 #include <stdarg.h>
 #include <stdio.h>
+
+#ifdef HAVE_UCONTEXT_H
+# include <ucontext.h>
+#endif
+
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
 #endif
-- 
1.9.1