Install symlinks with same suffix and extension as installed file

Move symlink installation into the binaryDecorator so that it can
access the suffix and extension when installing symlinks.  Also
consolidates the symlink and symlink_preferred_arch handling.

Test: m -j clang, ls -l out/host/windows-x86/bin/clang++.exe
Change-Id: I1204afb71fac87b276bd6b625b52ee21274855a0