Introduce ZLIBNG_ENABLE_TESTS

This patch adds the ability to run zlib-ng test suite against the
original zlib as follows:

    cmake -DZLIB_COMPAT=ON -DZLIBNG_ENABLE_TESTS=OFF .
    make
    LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu make test

The benefit of this is that modifications to the original zlib can be
tested with a more extensive zlib-ng's testsuite, and the assumptions
that the zlib-ng tests make can be validated against the original zlib.

In addition to a number of tests that exercise purely zlib-ng specific
API, there are a few that expect zlib-ng specific behavior from the
original zlib API:

- deflate() (obviously) emits different streams
- zlib-ng's deflatePrime() can take more than 16 bits
- zVersion() returns a different string

Adjust or disable the respective tests for ZLIBNG_ENABLE_TESTS=OFF.

1 files changed, 1 insertions, 0 deletions

diff --git a/README.md b/README.md
index c2254a4328..a1218d44d0 100644
--- a/README.md
+++ b/README.md
@@ -228,6 +228,7 @@ Advanced Build Options
 | WITH_INFLATE_STRICT             |                       | Build with strict inflate distance checking                         | OFF                    |
 | WITH_INFLATE_ALLOW_INVALID_DIST |                       | Build with zero fill for inflate invalid distances                  | OFF                    |
 | INSTALL_UTILS                   |                       | Copy minigzip and minideflate during install                        | OFF                    |
+| ZLIBNG_ENABLE_TESTS             |                       | Test zlib-ng specific API                                           | ON                     |
 
 
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