Disables debuggerd integration unless building for android.
Bug: 31559095
Test: Diff out/soong/build.ninja before/after, only change is moving
linker's libdebuggerd_client static lib to the beginning of the
list.
Test: lunch aosp_arm64-eng; mmma -j bionic
Change-Id: I62e725f7a9b98b7fe31637d0a835fd5846b0aff0
Extract linker executable specific code to linker_main.cpp;
this part of code does not have a place in libdl.a/so.
Bug: http://b/14998480
Bug: http://b/30706810
Test: mm && run bionic-unit-tests
Change-Id: I90f7475e93a919b0f9525da22928089ad35b8f6c