nova: PIC compatible syscall_5

Addressing must be PC-relative, so adapt the approach from the other
nova_x86_32 syscall bindings (description by @ssumpf):

  Use call to push the current IP on the stack and add the distance of
  label 0 and label 1 in order to determine the return address, which
  NOVA requires in edx.

The bug only showed up with "-O0" in libc.lib.so in form of a unwanted
text relocation.

Fixes #1721

repos/base-nova/include/spec/32bit/nova/syscalls.h

@@ -166,9 +166,12 @@ namespace Nova {
 		asm volatile ("  push %%ebx;"
 
 		              "  mov %%ecx, %%ebx;"
-		              "  movl %%esp, %%ecx;"
+		              "  mov %%esp, %%ecx;"
-		              "  movl $1f, %%edx;"
 
+		              "  call 0f;"
+		              "0:"
+		              "  addl $(1f-0b), (%%esp);"
+		              "  mov (%%esp), %%edx;"
 		              "sysenter;"
 		              "1:"