src/rt/arch/i386/morestack.S: call rust_stack_exhausted via plt

This prevents a relocation in the text section. Text relocations are incompatible with hardened kernels. rust-lang#5714

Author: srwalter

src/rt/arch/i386/morestack.S

@@ -75,15 +75,14 @@
 #else
 #if defined(__linux__) || defined(__FreeBSD__)
 #define MORESTACK __morestack
-#define EXHAUSTED rust_stack_exhausted
+#define EXHAUSTED rust_stack_exhausted@plt
 #else
 #define MORESTACK ___morestack
 #define EXHAUSTED _rust_stack_exhausted
 #endif
 #endif
 
 .globl MORESTACK
-.globl EXHAUSTED
 
 // FIXME: What about __WIN32__?
 #if defined(__linux__) || defined(__FreeBSD__)
@@ -138,7 +137,7 @@ MORESTACK:
 
  // re-align the stack
  subl $12,%esp
- calll EXHAUSTED
+ call EXHAUSTED
  // the exhaustion function guarantees that it can't return
 
 .cfi_endproc