[ELF] - Use error() instead of fatal() during relaxation of R_X86_64_GOTTPOFF

This is last known noticable fatal() in target.cpp.
We also have other ones for unknown relocations or
creating unknown targets, but that one can be just error I think.

Used yaml2obj to generate test.

Differential revision: https://reviews.llvm.org/D28049

llvm-svn: 290335
diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index c0fcd95..edae7c6 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -799,7 +799,7 @@
     memcpy(Inst, "\x48\xc7", 2);
     *RegSlot = 0xc0 | Reg;
   } else {
-    fatal(getErrorLocation(Loc - 3) +
+    error(getErrorLocation(Loc - 3) +
           "R_X86_64_GOTTPOFF must be used in MOVQ or ADDQ instructions only");
   }