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

fusl/src/string/strcasecmp.c

Index: fusl/src/string/strcasecmp.c
diff --git a/fusl/src/string/strcasecmp.c b/fusl/src/string/strcasecmp.c
new file mode 100644
index 0000000000000000000000000000000000000000..3cd5f2d0243e5b5ce5048282e03321763509db67
--- /dev/null
+++ b/fusl/src/string/strcasecmp.c
@@ -0,0 +1,17 @@
+#include <strings.h>
+#include <ctype.h>
+#include "libc.h"
+
+int strcasecmp(const char *_l, const char *_r)
+{
+	const unsigned char *l=(void *)_l, *r=(void *)_r;
+	for (; *l && *r && (*l == *r || tolower(*l) == tolower(*r)); l++, r++);
+	return tolower(*l) - tolower(*r);
+}
+
+int __strcasecmp_l(const char *l, const char *r, locale_t loc)
+{
+	return strcasecmp(l, r);
+}
+
+weak_alias(__strcasecmp_l, strcasecmp_l);