linker: Fix ARM_R_COPY relocations

Per http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
Section 4.7.1.10, ARM_R_COPY relocations are only suppose to reference shared
libraries, not the executable itself.  When resolving an R_ARM_COPY symbol,
ensure we don't look in our own symbol.

This partially addresses
http://code.google.com/p/android/issues/detail?id=28598 .  After this
patch, the printfs generated by the test program are:

global = 0x42 (0x401c7000)
global = 0x42 (0x11000)

before, the output was:

global = 0x42 (0x40071000)
global = 0x0 (0x11000)

I'm still not very happy with this patch, but I think it's an improvement
over where we were at before.

This change was modeled after https://android-review.googlesource.com/38871

Change-Id: Id7ad921e58395e76a36875bcc742ec5eeba53f08