Nobody needs to change a language standard for 9 lines of code. When you really want to use a hash map, its likely that you care about performance, so you don't want to use a generic implementation anyway.
> or a at least a community consensus about which one you pick
There is a hash table API in POSIX:
GNU libc: https://sourceware.org/glibc/manual/latest/html_node/Hash-Search-Function.html
Linux hsearch(3): https://man7.org/linux/man-pages/man3/hsearch.3.html
hsearch(3posix): https://www.man7.org/linux/man-pages/man3/hcreate.3p.html
Sure its not impossible for C to get that, but at the same time, they are trying to write git not fix C.
* My point is, that hash maps and data structures like that are clearly not the priority of C or they would **exist by now.
** by exist I mean either in C standard, or a at least a community consensus about which one you pick, unless you need something specific.