core/CMakeLists: Make some warnings errors

Makes our error coverage a little more consistent across the board by
applying it to Linux side of things as well. This also makes it more
consistent with the warning settings in other libraries in the project.

This also updates httplib to 0.7.9, as there are several warning
cleanups made that allow us to enable several warnings as errors.

externals/CMakeLists.txt

@@ -90,6 +90,9 @@ if (ENABLE_WEB_SERVICE)
     target_include_directories(httplib INTERFACE ./httplib)
     target_compile_definitions(httplib INTERFACE -DCPPHTTPLIB_OPENSSL_SUPPORT)
     target_link_libraries(httplib INTERFACE ${OPENSSL_LIBRARIES})
+    if (WIN32)
+        target_link_libraries(httplib INTERFACE crypt32 cryptui ws2_32)
+    endif()
 endif()
 
 # Opus