Actually set the header guard in "linux-syscalls.h".

Spotted while merging a MIPS change.

Change-Id: I36fb5a07d0bba0c117e9fe9733957bd37ca4b4c0
diff --git a/libc/include/sys/linux-syscalls.h b/libc/include/sys/linux-syscalls.h
index a60d3fa..de64c6b 100644
--- a/libc/include/sys/linux-syscalls.h
+++ b/libc/include/sys/linux-syscalls.h
@@ -1,5 +1,6 @@
 /* auto-generated by gensyscalls.py, do not touch */
 #ifndef _BIONIC_LINUX_SYSCALLS_H_
+#define _BIONIC_LINUX_SYSCALLS_H_
 
 #if !defined __ASM_ARM_UNISTD_H && !defined __ASM_I386_UNISTD_H && !defined __ASM_MIPS_UNISTD_H
 #if defined __arm__ && !defined __ARM_EABI__ && !defined __thumb__
diff --git a/libc/tools/gensyscalls.py b/libc/tools/gensyscalls.py
index 947e444..edad792 100755
--- a/libc/tools/gensyscalls.py
+++ b/libc/tools/gensyscalls.py
@@ -425,7 +425,8 @@
         D( "generating "+path )
         fp = create_file( path )
         fp.write( "/* auto-generated by gensyscalls.py, do not touch */\n" )
-        fp.write( "#ifndef _BIONIC_LINUX_SYSCALLS_H_\n\n" )
+        fp.write( "#ifndef _BIONIC_LINUX_SYSCALLS_H_\n" )
+        fp.write( "#define _BIONIC_LINUX_SYSCALLS_H_\n\n" )
         fp.write( "#if !defined __ASM_ARM_UNISTD_H && !defined __ASM_I386_UNISTD_H && !defined __ASM_MIPS_UNISTD_H\n" )
         fp.write( "#if defined __arm__ && !defined __ARM_EABI__ && !defined __thumb__\n" )
         fp.write( "  #  define __NR_SYSCALL_BASE 0x900000\n" )