[BOLT] Don't choke on nobits symbols (#136384)

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -1055,10 +1055,11 @@ void RewriteInstance::discoverFileObjects() {
       continue;
     }
 
-    if (!Section->isText()) {
+    if (!Section->isText() || Section->isVirtual()) {
       assert(SymbolType != SymbolRef::ST_Function &&
              "unexpected function inside non-code section");
-      LLVM_DEBUG(dbgs() << "BOLT-DEBUG: rejecting as symbol is not in code\n");
+      LLVM_DEBUG(dbgs() << "BOLT-DEBUG: rejecting as symbol is not in code or "
+                           "is in nobits section\n");
       registerName(SymbolSize);
       continue;
     }

bolt/test/X86/nobits-symbol.s

@@ -0,0 +1,24 @@
+## Check that llvm-bolt doesn't choke on symbols defined in nobits sections.
+
+# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown %s -o %t.o
+# RUN: %clang %cflags %t.o -o %t.exe
+# RUN: llvm-bolt %t.exe -o %t
+#
+
+  .type            symbol_in_nobits,@object
+  .section        .my.nobits.section,"awx",@nobits
+  .globl           symbol_in_nobits
+  .p2align         4, 0x0
+symbol_in_nobits:
+  .zero  0x100000
+  .size   symbol_in_nobits, 0x100000
+
+	.text
+  .globl main
+  .type main, %function
+main:
+	.cfi_startproc
+.LBB06:
+  retq
+	.cfi_endproc
+.size main, .-main