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

fusl/src/process/execvp.c

+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+#include "libc.h"
+
+extern char **__environ;
+
+int __execvpe(const char *file, char *const argv[], char *const envp[])
+{
+        const char *p, *z, *path = getenv("PATH");
+        size_t l, k;
+        int seen_eacces = 0;
+
+        errno = ENOENT;
+        if (!*file) return -1;
+
+        if (strchr(file, '/'))
+                return execve(file, argv, envp);
+
+        if (!path) path = "/usr/local/bin:/bin:/usr/bin";
+        k = strnlen(file, NAME_MAX+1);
+        if (k > NAME_MAX) {
+                errno = ENAMETOOLONG;
+                return -1;
+        }
+        l = strnlen(path, PATH_MAX-1)+1;
+
+        for(p=path; ; p=z) {
+                char b[l+k+1];
+                z = strchr(p, ':');
+                if (!z) z = p+strlen(p);
+                if (z-p >= l) {
+                        if (!*z++) break;
+                        continue;
+                }
+                memcpy(b, p, z-p);
+                b[z-p] = '/';
+                memcpy(b+(z-p)+(z>p), file, k+1);
+                execve(b, argv, envp);
+                if (errno == EACCES) seen_eacces = 1;
+                else if (errno != ENOENT) return -1;
+                if (!*z++) break;
+        }
+        if (seen_eacces) errno = EACCES;
+        return -1;
+}
+
+int execvp(const char *file, char *const argv[])
+{
+        return __execvpe(file, argv, __environ);
+}
+
+weak_alias(__execvpe, execvpe);