I considered using simple library names like "test.so" instead of "libtest.so".
However, that would imply linking with the full path name "lib/fexl/test.so"
instead the standard "-ltest".  Problem is, when you don't use the "-l" form,
things don't work well when you run the program from outside the build
directory, because it doesn't use the library search path rules such as
/etc/ld.so.conf and LD_LIBRARY_PATH.  So I'm sticking with "-l".