Turn off -Werror for gcc 4.2.1

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Summary

As part of marching gcc 4.2.1 out of the tree, turn off -Werror on gcc 4.2.1
compiles by default. It generates too many false positives and breaks CI
for no benefit.

Discussed on: arch@

this was spurred on by the stupid const cast away DECONST patches.

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sys/conf/kern.pre.mk

96 ↗

(On Diff #61162)

here and below need to kill trailing ).

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sys/conf/kern.pre.mk

97 ↗

(On Diff #61162)

convention says there should be a tab here (and below) will do (from allanjude)

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nits noted

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Passes MALTA kernel build.
Passes MALTA64 kernel build.
Passes powerpc GENERIC build.

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add Turn off -Werror for gcc 4.2.1 for userland