add support for C11 Annex K qsort_s()

standard defined re-entrant variant of qsort().
Unfortunately, Annex K is optional.

.github/workflows/dev-short-tests.yml

@@ -693,7 +693,7 @@ jobs:
       - name: Install musl-tools
         run: |
           sudo apt install -y musl-tools
-      - name: Compile the project with musl-gcc
+      - name: Compile with musl-gcc and test-zstd
         run: |
           CC=musl-gcc CFLAGS="-Werror -O3" CPPFLAGS=-DZDICT_QSORT=ZDICT_QSORT_C90 make -j -C tests test-zstd V=1