Require fmt-5.3

Drop support for pre pkg-config fmt.

Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

build/premake/extern_libs5.lua

@@ -308,26 +308,9 @@ extern_lib_defs = {
 		compile_settings = function()
 			if os.istarget("windows") then
 				add_default_include_paths("fmt")
-			elseif os.istarget("macosx") then
+			else
 				pkgconfig.add_includes("fmt")
 			end
-
-			-- With Linux & BSD, we assume that fmt is installed in a standard location.
-			--
-			-- It would be nice to not assume, and to instead use pkg-config: however that
-			-- requires fmt 5.3.0 or greater.
-			--
-			-- Unfortunately (at the time of writing) only 92 out of 114 (~80.7%) of distros
-			-- that provide a fmt package meet this, according to
-			-- https://repology.org/badge/vertical-allrepos/fmt.svg?minversion=5.3
-			--
-			-- Whilst that might seem like a healthy majority, this does not include the 2018
-			-- Long Term Support and 2019.10 releases of Ubuntu - not only popular and widely
-			-- used as-is, but which are also used as a base for other popular distros (e.g.
-			-- Mint).
-			--
-			-- When fmt 5.3 (or better) becomes more widely used, then we can safely use the
-			-- same line as we currently use for osx
 		end,
 		link_settings = function()
 			if os.istarget("windows") then
@@ -337,13 +320,8 @@ extern_lib_defs = {
 					dbg_suffix = "d",
 					no_delayload = 1,
 				})
-			elseif os.istarget("macosx") then
-				-- See comment above as to why this is not also used on Linux or BSD.
-				pkgconfig.add_links("fmt")
 			else
-				add_default_links({
-					unix_names = { "fmt" },
-				})
+				pkgconfig.add_links("fmt")
 			end
 		end
 	},