In 2020, SHA-1 practically broken in chosen-prefix collision (CP-collision). Can double SHA-1 hashing prevent CP-collision?
a. No such double hashing doesn't do a bit of good. Anything which collides after a single hash will definetly collide after a double hash. It preserves all collisions and adds new ones.

We might consider other constructions which may provide some strength e.g $H(H(m) || m)$ however:

b. We have no need for any such double hashing of SHA1 as we have newer better hash functions. Most notably we have SHA3 which is by all accounts far from being broken