runtime: remove unused frag calculation in ASAN poisoning

[qinlonglong123]

The variable frag is computed but never used in the ASAN poisoning
logic below. The code calculates the fragment size between the actual
allocation slot and the requested size, optionally adjusting for the
malloc header, but the result is discarded. Remove this dead code
since asanpoison and asanunpoison only require size and asanRZ.

[gopherbot]

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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[gopherbot]

Message from Ian Lance Taylor:

Patch Set 1:

(2 comments)

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