[snapshot] Add '.note.GNU-stack' marker section for ELF snapshots

This snapshot adds a marker section to the output assembly of
mksnapshot. Omitting this section can imply an executable stack, which
can result in linker warnings.

R=jgruber@chromium.org

Change-Id: I6f5dacb24de3a852faf6ce0caf18c32b499ba5a9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1687669
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62504}

src/snapshot/embedded/platform-embedded-file-writer-generic.cc

@@ -127,7 +127,15 @@ void PlatformEmbeddedFileWriterGeneric::DeclareExternalFilename(
   fprintf(fp_, ".file %d \"%s\"\n", fileid, fixed_filename.c_str());
 }
 
-void PlatformEmbeddedFileWriterGeneric::FileEpilogue() {}
+void PlatformEmbeddedFileWriterGeneric::FileEpilogue() {
+  // Omitting this section can imply an executable stack, which is usually
+  // a linker warning/error. C++ compilers add these automatically, but
+  // compiling assembly requires the .note.GNU-stack section to be inserted
+  // manually.
+  // Additional documentation:
+  // https://wiki.gentoo.org/wiki/Hardened/GNU_stack_quickstart
+  fprintf(fp_, ".section .note.GNU-stack,\"\",%%progbits\n");
+}
 
 int PlatformEmbeddedFileWriterGeneric::IndentedDataDirective(
     DataDirective directive) {