libebml: don't rely on make -e, obey LDFLAGS

We need to obey LDFLAGS to get the correct hash style for external toolchains,
and passing vars explicitly is better than relying on implicitly overriding
everything blindly from the environment.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
(cherry picked from commit 64d874f768207a8a1e27a5c6edd3abe90607af03)
Signed-off-by: Armin Kuster <akuster808@gmail.com>