Bump CMAKE_CXX_STANDARD to 23 and fix code

ftparchive/contents.h failed with operator< defined only,
so define operator<=> instead.

The operator and FileCopyType constructor both had a warning
about not throwing and adding a noexcept, so add one

1 files changed, 1 insertions, 1 deletions

diff --git a/ftparchive/contents.h b/ftparchive/contents.h
index e23191cd3..a78f9d5e9 100644
--- a/ftparchive/contents.h
+++ b/ftparchive/contents.h
@@ -27,7 +27,7 @@ class GenContents
    {
       const char *data;
       const char *c_str() const { return data; }
-      bool operator<(const StringInBlock &other) const { return strcmp(data, other.data) < 0; }
+      auto operator<=>(const StringInBlock &other) const noexcept { return strcmp(data, other.data); }
    };
    struct BigBlock
    {