Closed issue by pullmoll on void-packages repository

https://github.com/void-linux/void-packages/issues/18571

Description:
When building `ghc` there is a problem with duplicate `.debug_line` statements emitted into the assembler files because `ghc` seems to pass `-g` to `gas` also.

This makes `gas` create its own `.debug_line` statements in addition to what was there before, where the relevant ones are those created by `ghc`.

Now since `binutils` treats such duplicated `.debug_line` statements as a fatal error, we can no longer build `ghc`. I tried to turn the fatal error into a warning and it seems this is sufficient to get `ghc` built again. Here's my patch for `binutils`:
```
--- gas/dwarf2dbg.c     2019-09-09 15:19:43.000000000 +0200
+++ gas/dwarf2dbg.c     2020-01-26 16:02:37.951224098 +0100
@@ -2224,7 +2224,7 @@
   /* We can't construct a new debug_line section if we already have one.
      Give an error.  */
   if (all_segs && !empty_debug_line)
-    as_fatal ("duplicate .debug_line sections");
+    as_warn ("duplicate .debug_line sections");

   if ((!all_segs && emit_other_sections)
       || (!emit_other_sections && !empty_debug_line))
```
It would however be much better to fix `ghc` and make it strip `-g` from the flags passed to `gas`. I fail to find the place where calling the assembler and passing `CFLAGS` happens, though.