Unbreak math/parmetis everywhere except FreeBSD 8

There were two issues with the previous commit.
  - LDFLAGS wsa missing -L argument for libc++
  - The libc++.so file is not actually a library, it's a linker script.
    Specifying libc++.so in LIB_DEPENDS causes the port to fail when
    it tries to install libc++ twice since it fails to recognize
    libc++.so as a library.

This doesn't fix FreeBSD breakage because it seems that it's missing
the C99 math function symbols.


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@369649 35697150-7ecd-e111-bb59-0022644237b5
net/bmon: Unbreak on DF (Not all BSDs have "BSD" in their name)


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@369650 35697150-7ecd-e111-bb59-0022644237b5