flat.lds: discard .comment and .note

Compilers like gcc may place information like compiler versions, build IDs,
etc. into dedicate sections called .comment or .note. These sections may be
placed even before the entry point if the linker script does not specify how
these sections shall be handled. This can be problematic as it is assumed that
the beginning of the image is a 12-byte multiboot header, followed by the entry
point of the image. It has also been met that ignoring these sections in the
linker script leads to a very small bss_start (mostly <1K), which leads the test
program to crash when it tries to initialize its .bss section.

Discard these sections as these sections contain compiler/linker-specific
information which is mostyl useless at runtime.

Signed-off-by: Junjie Mao <[email protected]>

x86/flat.lds

@@ -20,6 +20,10 @@ SECTIONS
     .bss : { *(.bss) }
     . = ALIGN(4K);
     edata = .;
+
+    /DISCARD/ : {
+        *(.comment .comment.* .note .note.*)
+    }
 }
 
 ENTRY(start)