Reland r84802 with a fix - Disable ICF for Valgrind/ThreadSanitizer Release builds

Reland r84802 with a fix - Disable ICF for Valgrind/ThreadSanitizer Release builds

With ICF the linker merges identical functions into one block of assembly,
which leads to
a) wrong symbols for some functions - which is debugger/Valgrind-unfriendly
b) all ThreadSanitizer annotations end up being one function which makes TSan crazy.

Since we run release code (with -O1 -g) on Valgrind bots,
we have to disable ICF if release_valgrind_build!=0.

BUG=82114
TEST=linux_tsan trybot goes green
TEST=`gclient runhooks` with and w/o GYP_DEFINES="release_valgrind_build=1"
     and `grep "\-\-icf" base/base.target.mk`
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=84833

[bradn, 2011-05-10 19:45:19]

LGTM