port-arm/47401: armv6 targeted build uses instructions not available on armv6

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>Number:         47401
>Category:       port-arm
>Synopsis:       armv6 targeted build uses instructions not available on armv6
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 04 01:10:00 +0000 2013
>Originator:     Antti Kantee
>Release:        
>Organization:
>Environment:
>Description:
When compiling src/common/lib/libc/arch/arm/atomic with -march=armv6 (gas 
2.23), you get e.g. following errors:

atomic_add_64.S:42: Error: selected processor does not support ARM mode `ldrexd 
r0,[r4]'
atomic_add_64.S:45: Error: selected processor does not support ARM mode `strexd 
ip,r2,[r4]'
atomic_add_64.S:65: Error: selected processor does not support ARM mode `ldrexd 
r0,[r4]'
atomic_add_64.S:68: Error: selected processor does not support ARM mode `strexd 
ip,r0,[r4]'

Additionally, at least arm/include/lock.h has uses _ARM_ARCH_6_ in a similar 
inaccurate fashion with ldrexb.
>How-To-Repeat:

>Fix: