Add a "fork" of musl as //fusl.

fusl/src/stdio/fwrite.c

Index: fusl/src/stdio/fwrite.c
diff --git a/fusl/src/stdio/fwrite.c b/fusl/src/stdio/fwrite.c
new file mode 100644
index 0000000000000000000000000000000000000000..81ec271e1bcb7ba477f92c8af74e4cc159deb032
--- /dev/null
+++ b/fusl/src/stdio/fwrite.c
@@ -0,0 +1,37 @@
+#include "stdio_impl.h"
+#include <string.h>
+
+size_t __fwritex(const unsigned char *restrict s, size_t l, FILE *restrict f)
+{
+	size_t i=0;
+
+	if (!f->wend && __towrite(f)) return 0;
+
+	if (l > f->wend - f->wpos) return f->write(f, s, l);
+
+	if (f->lbf >= 0) {
+		/* Match /^(.*\n|)/ */
+		for (i=l; i && s[i-1] != '\n'; i--);
+		if (i) {
+			if (f->write(f, s, i) < i)
+				return i;
+			s += i;
+			l -= i;
+		}
+	}
+
+	memcpy(f->wpos, s, l);
+	f->wpos += l;
+	return l+i;
+}
+
+size_t fwrite(const void *restrict src, size_t size, size_t nmemb, FILE *restrict f)
+{
+	size_t k, l = size*nmemb;
+	FLOCK(f);
+	k = __fwritex(src, l, f);
+	FUNLOCK(f);
+	return k==l ? nmemb : k/size;
+}
+
+weak_alias(fwrite, fwrite_unlocked);