Externals: Update fmt to 7.1.0

Updates fmt to the latest release from 6.1.2

Externals/fmt/support/cmake/JoinPaths.cmake

@@ -0,0 +1,26 @@
+# This module provides function for joining paths
+# known from from most languages
+#
+# Original license:
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Explicit permission given to distribute this module under
+# the terms of the project as described in /LICENSE.rst.
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()

Externals/fmt/support/cmake/cxx14.cmake

@@ -48,17 +48,6 @@ endif ()
 
 set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG})
 
-# Check if variadic templates are working and not affected by GCC bug 39653:
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39653
-# Can be removed once gcc 4.4 support is dropped.
-check_cxx_source_compiles("
-  template <class T, class ...Types>
-  struct S { typedef typename S<Types...>::type type; };
-  int main() {}" SUPPORTS_VARIADIC_TEMPLATES)
-if (NOT SUPPORTS_VARIADIC_TEMPLATES)
-  set (SUPPORTS_VARIADIC_TEMPLATES OFF)
-endif ()
-
 # Check if user-defined literals are available
 check_cxx_source_compiles("
   void operator\"\" _udl(long double);

Externals/fmt/support/cmake/fmt.pc.in

@@ -1,11 +1,11 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=@CMAKE_INSTALL_PREFIX@
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
 
 Name: fmt
 Description: A modern formatting library
 Version: @FMT_VERSION@
-Libs: -L${libdir} -lfmt
+Libs: -L${libdir} -l@FMT_LIB_NAME@
 Cflags: -I${includedir}