modified build system + added musl_c build

scripts/check.sh

@@ -1,12 +1,15 @@
-#/bin/sh
+#!/bin/sh
+set -eu
+
+SOURCES_FILE=./sources.list
 
 while IFS= read -r url; do \
 [ -z "$url" ] && continue; \
 fname="$(printf '%s' "$url" | sed -E 's/[?#].*$//' | sed -E 's!.*/!!')"; \
-if [ -e "$(OUTDIR)/$fname" ]; then \
+if [ -e "./sources/$fname" ]; then \
 	printf "SKIP: %s (already exists)\n" "$fname"; \
 else \
 	printf "GET: %s -> %s\n" "$url" "$fname"; \
 	curl -o "./sources/$fname" "$url" || { printf "ERROR: failed to download %s\n" "$url"; exit 1; }; \
 fi; \
-done < ${SOURCES_FILE}; \
+done < "$SOURCES_FILE"; \