Avoid messing with dummy functions in delocate.go.
With some optimisation settings, Clang was loading
BORINGSSL_bcm_text_hash with AVX2 instructions, which weren't getting
translated correctly. This seems to work and is less fragile.
The compiler just emits an leaq here. This is because it knows the
symbol is hidden (in the shared library sense), so it needn't go through
GOTPCREL. The assembler would have added a relocation, were the symbol
left undefined, but since we define the symbol later on, it all works
out without a relocation.
Were the symbol not hidden, the compiler would have emitted a movq by
way of GOTPCREL, but we can now translate those away anyway.
Change-Id: I442a22f4f8afaadaacbab7044f946a963ebfc46c
Reviewed-on: https://boringssl-review.googlesource.com/15384
Reviewed-by: Adam Langley <agl@google.com>