-Wl,--push-state,--no-as-needed,-lc,--pop-state forces libc back into
DT_NEEDED for libraries that reach it only through libhttrack: the
libhtsjava JNI wrapper and the libtest callback examples. The flag is
GNU-ld-specific; Apple's ld rejects it ("ld: unknown options:
--push-state --no-as-needed --pop-state"), breaking the macOS build, and
doesn't need it (every dylib links libSystem anyway).
Probe it once with AX_CHECK_LINK_FLAG and emit it via LIBC_FORCE_LINK
only where the linker accepts it. On GNU/Linux the flag is still applied
and libc.so.6 stays in DT_NEEDED, so behavior is unchanged there.
Signed-off-by: Xavier Roche <roche@httrack.com>
d3eecbf211