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

fusl/src/process/fexecve.c

Index: fusl/src/process/fexecve.c
diff --git a/fusl/src/process/fexecve.c b/fusl/src/process/fexecve.c
new file mode 100644
index 0000000000000000000000000000000000000000..6507b42949c915e757bfa71935388a0ea4e0a15d
--- /dev/null
+++ b/fusl/src/process/fexecve.c
@@ -0,0 +1,13 @@
+#include <unistd.h>
+#include <errno.h>
+
+void __procfdname(char *, unsigned);
+
+int fexecve(int fd, char *const argv[], char *const envp[])
+{
+	char buf[15 + 3*sizeof(int)];
+	__procfdname(buf, fd);
+	execve(buf, argv, envp);
+	if (errno == ENOENT) errno = EBADF;
+	return -1;
+}