toolchain/50841: MKREPRO: debug builds not reproducible

[Thomas Klausner <wiz%NetBSD.org@localhost>]

>Number:         50841
>Category:       toolchain
>Synopsis:       MKREPRO: debug builds not reproducible
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 23 15:30:00 +0000 2016
>Originator:     Thomas Klausner
>Release:        NetBSD 7.99.26
>Organization:
Curiosity is the very basis of education and if you tell me that 
curiosity killed the cat, I say only that the cat died nobly.
- Arnold Edinborough
>Environment:
	
	
Architecture: x86_64
Machine: amd64
>Description:
Building twice with different source and obj dirs and MKREPRO set gives
slightly different files.

One example:
# diffoscope amd64.gcc.20160223/bin/ls amd64.gcc.20160223v2/bin/ls |less
--- amd64.gcc.20160223/bin/ls
+++ amd64.gcc.20160223v2/bin/ls
|-- objdump --disassemble --full-contents {}
| @@ -1422,15 +1422,15 @@
|   05b0 d2c4aeb0 786a07d9 6d1f91f7 24990c92  ....xj..m...$...
|   05c0 c59586c8 c22b551a ae0c3a38 86db6a6f  .....+U...:8..jo
|   05d0 46d8bdb2 826dafe9 9748d765 c5f8c2ad  F....m...H.e....
|   05e0 9735a71f ae525d39 993def72 c77fc31c  .5...R]9.=.r....
|   05f0 9ff4e549 49efc9ae dc36462b dbfb1749  ...II....6F+...I
|   0600 bf4618                               .F.
|  Contents of section .gnu_debuglink:
| - 0000 6c732e64 65627567 00000000 4a1a935e  ls.debug....J..^
| + 0000 6c732e64 65627567 00000000 30af7a9d  ls.debug....0.z.
|
|  Disassembly of section .init:
|
|  0000000000401140 <_init>:
|    401140:    48 83 ec 08             sub    $0x8,%rsp
|    401144:    e8 cc 04 00 00          callq  401615 <___start+0x16f>
|    401149:    48 83 c4 08             add    $0x8,%rsp
|
>How-To-Repeat:
See above.
>Fix:
please.

>Unformatted: