fix(ci): GNU-extension array literal + macOS-only basename_r

Two more GCC errors from CI on Ubuntu:

- `cgi.cpp` was passing `(char *[]){NULL}` as argv to `execvp` — a C99
  compound literal that GCC accepts in C but not in C++ (the addresses
  of the temporary array are then dereferenced by execvp). Replaced
  with a proper `char* argv[]` local that carries the script path as
  argv[0] (which is what execvp expects anyway).
- `mime_types.cpp::choiceMimeType` called Apple-only `basename_r`, with
  `PATH_MAX` from `<libgen.h>`, but the result `bname` was never used.
  Deleted the dead code; the function only needs `path.find_last_of('.')`.

Author: awbx

src/http/cgi.cpp

@@ -74,7 +74,8 @@ pid_t CGI::spawn(int *fds, const int &fileno) {
 
 		init();
 		setenv();
-		execvp(_scriptFileName.c_str(), (char *[]){NULL});
+		char *argv[] = { const_cast<char *>(_scriptFileName.c_str()), NULL };
+		execvp(_scriptFileName.c_str(), argv);
 		perror("execvp");
 		exit(1);
 	}

src/http/mime_types.cpp

@@ -117,20 +117,11 @@ MimeType::MimeType(void) {
 	(*this)[""] = DEFAULT_MIME_TYPE;
 }
 
-#include <libgen.h>
-
 MimeType::mapped_type &MimeType::choiceMimeType(const string &path) {
-	
-	char bname[PATH_MAX] = {0};
-	basename_r(path.c_str(), bname);
-
-	size_t idx = path.find_last_of('.');
-
+	const size_t idx = path.find_last_of('.');
 	if (idx == string::npos)
 		return (*this)[""];
-	string ext = path.substr(idx + 1);
-	
-	return (*this)[ext];
+	return (*this)[path.substr(idx + 1)];
 }
 
 MimeType::mapped_type &MimeType::operator[](const key_type &key) {