i#975: Hide symbols in the STATIC_LIBRARY build on Unix

This is accomplished by doing a partial link (ld -r) and then using
objcopy --localize-hidden.  In GNU visiblity lingo, "hidden" means
public outside the individual translation unit, and "local" means the
same thing as C static.

In particular, we need to hide our string routines and our getenv
implementation.

Re-enables linux.fib-static and -pie which now pass with STATIC_LIBRARY.

Review URL: https://codereview.appspot.com/7029052

git-svn-id: https://dynamorio.googlecode.com/svn/trunk@1821 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6