cmake: linker: ld: fix duplicate LINK_FLAGS

Original implementation of `toolchain_linker_finalize` duplicates
the `LINK_FLAGS` in the link command. This can cause some problems
like duplicate definitions when using link options like
`--whole-archive`.

This commit fixes it by removing the duplicate `LINK_FLAGS`.

Fixes #82281

Signed-off-by: Axel Le Bourhis <axel.lebourhis@nxp.com>