pass c strings to fmt

boost strings and filesystem paths used to be automatically converted,
but that doesn't happen anymore with fmt 9

src/output.cpp

@@ -44,7 +44,7 @@ void print_matches(const std::vector<search::match> &matches,
         {
             cout << termcolor::yellow;
         }
-        cout << format(translate("  In {0:s}: \n").str(),
+        cout << format(translate("  In {0:s}: \n").str().c_str(),
                        fs::relative(matches[0].filepath_epub));
         if (!opts.nocolor)
         {

src/search.cpp

@@ -44,8 +44,8 @@ std::vector<match> search(const fs::path &filepath,
                           const std::string_view regex, const settings &opts)
 {
     LOG(log::sev::info)
-        << format(R"(Starting search in {0:s} using regex "{1:s}")", filepath,
+        << format(R"(Starting search in {0:s} using regex "{1:s}")",
-                  regex);
+                  filepath.c_str(), regex);
     boost::regex::flag_type flags{};
 
     switch (opts.regex)

src/zip.cpp

@@ -55,7 +55,7 @@ std::vector<std::string> list(const fs::path &filepath)
                 << format(translate("File in {0:s} is damaged. "
                                     "Skipping in-EPUB file.\n")
                               .str()
-                              .data(),
+                              .c_str(),
                           filepath);
             continue;
         }