These are more like LIBS rather than LDFLAGS.
They are used just in one place,
so simply put them inline.
Also, use LDFLAGS provided by the user during actual link.
This helps users pass their own LDFLAGS.
For example, this is important on Gentoo,
where LDFLAGS='-Wl,-O1 -Wl,--as-needed' is passed by default.