Strip unit_tests on Linux 32-bit official builds.

Strip unit_tests on Linux 32-bit official builds.

This is a workaround to avoid the issues we're having with the linker
running out of memory, like:

out/Release/../../third_party/gold/gold32: fatal error:
out/Release/unit_tests: mmap: failed to allocate 1373799052 bytes for output file: Cannot allocate memory

Removing the debug symbols shrinks the binary to about 10% the original
size, which in turn reduces the build's max mmap usage (roughly measured
as going from about 2GB to about 600MB).

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=149575

[Lei Zhang, 2012-08-02 04:38:34]

lgtm

[kerz_google, 2012-08-02 04:39:08]

lgtm