Add compatibility for GCC-7.

In GCC-7 filesystem is in std::experimental.

src/CMakeLists.txt

@@ -3,7 +3,9 @@ include(GNUInstallDirs)
 find_package(PkgConfig REQUIRED)
 pkg_check_modules(cgicc REQUIRED IMPORTED_TARGET cgicc)
 find_package(nlohmann_json REQUIRED CONFIG)
-find_package(Filesystem REQUIRED)
+find_package(Filesystem REQUIRED COMPONENTS Final Experimental)
+
+configure_file(fs-compat.hpp.in fs-compat.hpp @ONLY)
 
 add_executable(${PROJECT_NAME} main.cpp)
 
@@ -14,6 +16,9 @@ target_sources(${PROJECT_NAME}
 unset(sources_src)
 unset(headers_src)
 
+target_include_directories(${PROJECT_NAME}
+  PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+
 target_link_libraries(${PROJECT_NAME}
   PRIVATE PkgConfig::cgicc nlohmann_json std::filesystem)
 

src/cgi.cpp

@@ -15,11 +15,11 @@
  */
 
 #include "cgi.hpp"
+#include "fs-compat.hpp"
 
 #include <cgicc/Cgicc.h>
 
 #include <exception>
-#include <filesystem>
 #include <fstream>
 #include <ios>
 #include <iostream>
@@ -42,8 +42,6 @@ using std::string_view;
 using std::stringstream;
 using std::vector;
 
-namespace fs = std::filesystem;
-
 entry_type parse_formdata()
 {
     entry_type entry;

src/fs-compat.hpp.in

@@ -0,0 +1,2 @@
+#include <@CXX_FILESYSTEM_HEADER@>
+namespace fs = @CXX_FILESYSTEM_NAMESPACE@;

src/main.cpp

@@ -15,14 +15,13 @@
  */
 
 #include "cgi.hpp"
+#include "fs-compat.hpp"
 #include "json.hpp"
 
-#include <filesystem>
 #include <iostream>
 
 using std::cout;
 
-namespace fs = std::filesystem;
 using namespace FediBlock;
 
 void print_debug(const entry_type &entry)