Fix build on macOS with newer P4 SDK versions by linking with the p4s…

…cript_cstub library, for salesforce#78

- The p4client library seems to have unconditional references to the P4Script machinery, even if that feature is not used by the application (in this case, p4-fusion). This causes linking errors (undefined references to sqlite, and curl functions)
- The p4script_cstub library seems to be an official solution for this situation, as it contains stubs (dummy, empty implementations) of all relevant functions

p4-fusion/CMakeLists.txt

@@ -45,10 +45,9 @@ target_link_libraries(p4-fusion PUBLIC
     client
     rpc
     supp
+    p4script_cstub
     ${OPENSSL_SSL_LIBRARIES}
     ${OPENSSL_CRYPTO_LIBRARIES}
-    p4script
-    p4script_c
     git2
     minitrace
 )