Add static. NFC.

llvm-svn: 295448
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 3c84036..79799f0 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1520,7 +1520,7 @@
 }
 
 template <class ELFT, class uintX_t>
-uintX_t setOffset(OutputSectionBase *Sec, uintX_t Off) {
+static uintX_t setOffset(OutputSectionBase *Sec, uintX_t Off) {
   if (Sec->Type == SHT_NOBITS) {
     Sec->Offset = Off;
     return Off;