Split fuzz tests during fuzz build

Only build fuzz tests in a fuzz build, and don't build other tests.

Keeps fuzz compilers from instrumenting other tests, which are not fuzzed.

Resolves #7232

tests/CMakeLists.txt

@@ -80,17 +80,22 @@ file(COPY
   data/signed_monero_tx
   DESTINATION data)
 
-add_subdirectory(core_tests)
-add_subdirectory(fuzz)
-add_subdirectory(crypto)
-add_subdirectory(functional_tests)
-add_subdirectory(performance_tests)
-add_subdirectory(core_proxy)
-add_subdirectory(unit_tests)
-add_subdirectory(difficulty)
-add_subdirectory(block_weight)
-add_subdirectory(hash)
-add_subdirectory(net_load_tests)
+if (CMAKE_BUILD_TYPE STREQUAL "fuzz" OR OSSFUZZ)
+  add_subdirectory(fuzz)
+else ()
+  add_subdirectory(core_tests)
+  add_subdirectory(fuzz)
+  add_subdirectory(crypto)
+  add_subdirectory(functional_tests)
+  add_subdirectory(performance_tests)
+  add_subdirectory(core_proxy)
+  add_subdirectory(unit_tests)
+  add_subdirectory(difficulty)
+  add_subdirectory(block_weight)
+  add_subdirectory(hash)
+  add_subdirectory(net_load_tests)
+endif()
+
 if (BUILD_GUI_DEPS)
   add_subdirectory(libwallet_api_tests)
 endif()