Do not emit .debug_pubnames on Linux

Nothing uses .debug_pubnames or .debug_pubtypes on Linux, so omit
these sections there.

Closes rust-lang#48762

src/rustllvm/RustWrapper.cpp

@@ -560,8 +560,23 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateCompileUnit(
     unsigned RuntimeVer, const char *SplitName) {
   auto *File = unwrapDI<DIFile>(FileRef);
 
+#if LLVM_VERSION_GE(8, 0)
+  DICompileUnit::DebugNameTableKind kind;
+#ifdef __linux__
+  kind = DICompileUnit::DebugNameTableKind::None;
+#else
+  kind = DICompileUnit::DebugNameTableKind::Default;
+#endif
+#endif
+
   return wrap(Builder->createCompileUnit(Lang, File, Producer, isOptimized,
-                                         Flags, RuntimeVer, SplitName));
+                                         Flags, RuntimeVer, SplitName,
+                                         DICompileUnit::DebugEmissionKind::FullDebug,
+                                         0, true, false
+#if LLVM_VERSION_GE(8, 0)
+                                         , kind
+#endif
+                                         ));
 }
 
 extern "C" LLVMMetadataRef

src/test/run-make-fulldeps/no-linux-pubnames/Makefile

@@ -0,0 +1,9 @@
+-include ../tools.mk
+
+# Test that -g doesn't emit .debug_pubnames on Linux.
+
+all:
+ifeq ($(UNAME),Linux)
+	$(RUSTC) -g main.rs
+	! readelf -WS $(TMPDIR)/main | grep -q debug_pubnames
+endif

src/test/run-make-fulldeps/no-linux-pubnames/main.rs

@@ -0,0 +1,12 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn main() {
+}