[ELF][MIPS] Add handling for __gnu_local_gp symbol

This symbol is a "fake" symbol like "_gp_disp" and denotes
the GOT + 0x7FF0 value.

llvm-svn: 259781
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index e4fb84f..c184d75 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -388,7 +388,7 @@
         // relocation too because that case is possible for executable file
         // linking only.
         continue;
-      if (Body == Config->MipsGpDisp)
+      if (Body == Config->MipsGpDisp || Body == Config->MipsLocalGp)
         // MIPS _gp_disp designates offset between start of function and gp
         // pointer into GOT therefore any relocations against it do not require
         // dynamic relocation.