Fix broken entries in COMPATIBILITY.suite.SYMLINKS

$(COMPATIBILITY.$(suite).ARCH_DIRS.$(m)) can contain multiple
arch directories, separated by spaces. This causes a single entry in
COMPATIBILITY.$(suite).SYMLINKS to contain a space.

Later on, COMPATIBILITY.$(suite).SYMLINKS is sorted, so that one entry
with a space will be broken up into two invalid entries (or really,
it already was two invalid entries but it's more obvious after the
sort moves them away from each other)

Instead, create a symlink per each arch folder.

Also optimize it slightly by moving the sort of
`HOST_SHARED_LIBRARY.FILES` out of the loop and using += for some
variables.

Bug: 405184090
Test: Presubmits
Change-Id: Ic683ea16e082e8d7bc994fe797e730b4911a0734