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

fusl/src/stdlib/ecvt.c

Index: fusl/src/stdlib/ecvt.c
diff --git a/fusl/src/stdlib/ecvt.c b/fusl/src/stdlib/ecvt.c
new file mode 100644
index 0000000000000000000000000000000000000000..797b664ecfebc0841a23bae84aa62a70c5359e41
--- /dev/null
+++ b/fusl/src/stdlib/ecvt.c
@@ -0,0 +1,20 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+
+char *ecvt(double x, int n, int *dp, int *sign)
+{
+	static char buf[16];
+	char tmp[32];
+	int i, j;
+
+	if (n-1U > 15) n = 15;
+	sprintf(tmp, "%.*e", n-1, x);
+	i = *sign = (tmp[0]=='-');
+	for (j=0; tmp[i]!='e'; j+=(tmp[i++]!='.'))
+		buf[j] = tmp[i];
+	buf[j] = 0;
+	*dp = atoi(tmp+i+1)+1;
+
+	return buf;
+}