#10 EXTERNAL_LIBRARY2(): progname_LDFLAGS

[Joerg Faschingbauer]

just hacking the ext-pthread module of the utile demo
package.

seems we need a way to pass LDFLAGS to a using
module/program. pthread are in the habit of requiring
not only to pass cflags/cxxflags, but also pass these
flags on the linker line (especially for c++).

this is no problem under linux so far because
ACX_PTHREAD adds the -pthread flag, and gcc knows how
to behave then. but it could be a problem if we move to
different architectures where the compiler is not as smart.