Tests cannot be run before installation

[awilfox]

Currently, if make in run src/tests/testbench before libguess is installed, it will fail to run due to a linker error:

make: Entering directory '/usr/src/aports/main/libguess/src/libguess-1.2/src/tests/testbench'
make[1]: Entering directory '/usr/src/aports/main/libguess/src/libguess-1.2/src/tests/testbench'
Error loading shared library libguess.so.1: No such file or directory (needed by ../guess_testharness)
Error relocating ../guess_testharness: libguess_determine_encoding: symbol not found
Fail: ar/cp1256
make[1]: *** [Makefile:24: ar/cp1256.run] Error 1
make[1]: Leaving directory '/usr/src/aports/main/libguess/src/libguess-1.2/src/tests/testbench'
make: *** [Makefile:9: run] Error 1
make: Leaving directory '/usr/src/aports/main/libguess/src/libguess-1.2/src/tests/testbench'