[LLD][COFF] Set __buildid symbol in both symbol tables on ARM64X (#126777)

Author: cjacek

lld/COFF/Writer.cpp

@@ -1215,9 +1215,11 @@ void Writer::createMiscChunks() {
     // if we're ultimately not going to write CodeView data to the PDB.
     buildId = make<CVDebugRecordChunk>(ctx);
     debugRecords.emplace_back(COFF::IMAGE_DEBUG_TYPE_CODEVIEW, buildId);
-    if (Symbol *buildidSym = ctx.symtab.findUnderscore("__buildid"))
-      replaceSymbol<DefinedSynthetic>(buildidSym, buildidSym->getName(),
-                                      buildId, 4);
+    ctx.forEachSymtab([&](SymbolTable &symtab) {
+      if (Symbol *buildidSym = symtab.findUnderscore("__buildid"))
+        replaceSymbol<DefinedSynthetic>(buildidSym, buildidSym->getName(),
+                                        buildId, 4);
+    });
   }
 
   if (config->cetCompat) {

lld/test/COFF/arm64x-buildid.s

@@ -0,0 +1,14 @@
+# REQUIRES: aarch64
+# RUN: llvm-mc -triple=aarch64-windows -filetype=obj -o %t-arm64.obj %s
+# RUN: llvm-mc -triple=arm64ec-windows -filetype=obj -o %t-arm64ec.obj %s
+
+# RUN: lld-link -machine:arm64x -dll -noentry %t-arm64.obj %t-arm64ec.obj -debug -build-id -Brepro -out:%t.dll
+# RUN: llvm-readobj --hex-dump=.test %t.dll | FileCheck %s
+# CHECK: 0x180003000 3c100000 3c100000
+
+.section .test,"dr"
+.rva __buildid
+
+.section .bss,"bw",discard,__buildid
+.global __buildid
+__buildid: