Include path for preprocessed assembly sources (`.S`)

Summary

The include path for preprocessed assembly sources (.S) should be aligned with C sources (.c) and Cmm sources (.cmm) and Haskell sources with CPP (.hs).

In particular, the LEADING_UNDERSCORE macro defined in rts (ghcautoconf.h or ghcconfig.h) would be useful in assembly source.

Steps to reproduce

$ cat foo.c
#include "ghcconfig.h"
$ cat foo.cmm
#include "ghcconfig.h"
$ cat foo.S
#include "ghcconfig.h"
$ ghc -c foo.cmm  # OK
$ ghc -c foo.c    # OK
$ ghc -c foo.S
foo.S:1:10: error:  fatal error: 'ghcconfig.h' file not found
  |
1 | #include "ghcconfig.h"
  |          ^

#include "ghcconfig.h"
         ^~~~~~~~~~~~~
1 error generated.
`gcc' failed in phase `Assembler'. (Exit code: 1)

Expected behavior

ghc -c foo.S should assemble.

Environment

GHC version used: 9.11.20240518 (bb40244e)
Operating System: macOS
System Architecture: AArch64

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