"httrack -W" should ask a question, flush stdout, read the answer; it does so
for the project name, forgets to do so for the base path, the proxy and
possibly more (I stopped checking), which happens to work on glibc but breaks
musl-based distributions such as void, alpine, ...

IMHO it's a lot easier to just unbuffer stdout, ie

diff --git a/src/htshelp.c b/src/htshelp.c
index e51e498..8095c12 100644
--- a/src/htshelp.c
+++ b/src/htshelp.c
@@ -200,6 +200,7 @@ void help_wizard(httrackp * opt) {
   printf("To see the option list, enter a blank line or try httrack
--help\n");
   //
   // Project name
+  setbuf(stdout, NULL);
   while(strnotempty(projname) == 0) {
     printf("\n");
     printf("Enter project name :");