libfmt 10 changed the API, requiring a few adjustments to the codebase.
This backports the upstream fixes for building against libfmt 10.

Bug: https://bugs.gentoo.org/906074

--- a/src/SongPrint.cxx
+++ b/src/SongPrint.cxx
@@ -24,6 +24,7 @@
 #include "TagPrint.hxx"
 #include "client/Response.hxx"
 #include "fs/Traits.hxx"
+#include "lib/fmt/AudioFormatFormatter.hxx"
 #include "time/ChronoUtil.hxx"
 #include "util/StringBuffer.hxx"
 #include "util/UriUtil.hxx"
@@ -93,7 +94,7 @@ song_print_info(Response &r, const LightSong &song, bool base) noexcept
 		time_print(r, "Last-Modified", song.mtime);
 
 	if (song.audio_format.IsDefined())
-		r.Fmt(FMT_STRING("Format: {}\n"), ToString(song.audio_format));
+		r.Fmt(FMT_STRING("Format: {}\n"), song.audio_format);
 
 	tag_print_values(r, song.tag);
 
@@ -116,7 +117,7 @@ song_print_info(Response &r, const DetachedSong &song, bool base) noexcept
 		time_print(r, "Last-Modified", song.GetLastModified());
 
 	if (const auto &f = song.GetAudioFormat(); f.IsDefined())
-		r.Fmt(FMT_STRING("Format: {}\n"), ToString(f));
+		r.Fmt(FMT_STRING("Format: {}\n"), f);
 
 	tag_print_values(r, song.GetTag());
 
--- a/src/TagPrint.cxx
+++ b/src/TagPrint.cxx
@@ -21,7 +21,6 @@
 #include "tag/Tag.hxx"
 #include "tag/Settings.hxx"
 #include "client/Response.hxx"
-#include "util/StringView.hxx"
 
 #include <fmt/format.h>
 
@@ -35,7 +34,7 @@ tag_print_types(Response &r) noexcept
 }
 
 void
-tag_print(Response &r, TagType type, StringView value) noexcept
+tag_print(Response &r, TagType type, std::string_view value) noexcept
 {
 	r.Fmt(FMT_STRING("{}: {}\n"), tag_item_names[type], value);
 }
--- a/src/TagPrint.hxx
+++ b/src/TagPrint.hxx
@@ -21,6 +21,7 @@
 #define MPD_TAG_PRINT_HXX
 
 #include <cstdint>
+#include <string_view>
 
 enum TagType : uint8_t;
 
@@ -32,7 +33,7 @@ void
 tag_print_types(Response &response) noexcept;
 
 void
-tag_print(Response &response, TagType type, StringView value) noexcept;
+tag_print(Response &response, TagType type, std::string_view value) noexcept;
 
 void
 tag_print(Response &response, TagType type, const char *value) noexcept;
--- a/src/TimePrint.cxx
+++ b/src/TimePrint.cxx
@@ -36,5 +36,5 @@ time_print(Response &r, const char *name,
 		return;
 	}
 
-	r.Fmt(FMT_STRING("{}: {}\n"), name, s);
+	r.Fmt(FMT_STRING("{}: {}\n"), name, s.c_str());
 }
--- a/src/command/PlayerCommands.cxx
+++ b/src/command/PlayerCommands.cxx
@@ -28,6 +28,7 @@
 #include "Partition.hxx"
 #include "Instance.hxx"
 #include "IdleFlags.hxx"
+#include "lib/fmt/AudioFormatFormatter.hxx"
 #include "util/StringBuffer.hxx"
 #include "util/ScopeExit.hxx"
 #include "util/Exception.hxx"
@@ -185,7 +186,7 @@ handle_status(Client &client, [[maybe_unused]] Request args, Response &r)
 
 		if (player_status.audio_format.IsDefined())
 			r.Fmt(FMT_STRING(COMMAND_STATUS_AUDIO ": {}\n"),
-			      ToString(player_status.audio_format));
+			      player_status.audio_format);
 	}
 
 #ifdef ENABLE_DATABASE
-- 
2.39.2