Replace strdupa with strdup

Strdupa has potential to be unsafe thanks to the possibly unbound stack
usage. It also generates warnings when compiled on musl. This commit
therefore replaces it with properly checked heap allocation using
strdup.

Fixes bazelbuild#15729

src/main/tools/linux-sandbox-pid1.cc

@@ -146,8 +146,18 @@ static int CreateTarget(const char *path, bool is_directory) {
   }
 
   // Create the parent directory.
-  if (CreateTarget(dirname(strdupa(path)), true) < 0) {
-    DIE("CreateTarget %s", dirname(strdupa(path)));
+  {
+    char *buf, *dir;
+
+    if (!(buf = strdup(path)))
+      DIE("strdup");
+
+    dir = dirname(buf);
+    if (CreateTarget(dir, true) < 0) {
+      DIE("CreateTarget %s", dir);
+    }
+
+    free(buf);
   }
 
   if (is_directory) {