ssh2: Disable zlib detection

This seems to only be used with the OpenSSL backend (which we plan to
drop).

libgit2 already use builtin ZLIB, I'm not even sure we if it would be
used in libssh2 (we only use libssh2 to provide git ssh access, and git
already compress objects.

tools/git2.py

@@ -27,6 +27,8 @@ def build_library(env, deps):
         "LIBSSH2_LIBRARY": deps[-1],
         "USE_WINHTTP": 0,
         "STATIC_CRT": env.get("use_static_cpp", True),
+        "CMAKE_DISABLE_FIND_PACKAGE_ZLIB": 1,
+        "CMAKE_DISABLE_FIND_PACKAGE_OPENSSL": 1,
     }
 
     if env["platform"] != "windows":

tools/ssh2.py

@@ -12,6 +12,8 @@ def build_library(env, deps):
         "BUILD_EXAMPLES": 0,
         "BUILD_TESTING": 0,
         "BUILD_SHARED_LIBS": 0,
+        "CMAKE_DISABLE_FIND_PACKAGE_ZLIB": 1,
+        "CMAKE_DISABLE_FIND_PACKAGE_OPENSSL": 1,
         "CRYPTO_BACKEND": "OpenSSL",
     }