CI: Use pinned Rust version

Author: Turbo87

.github/workflows/main.yml

@@ -5,12 +5,16 @@ on:
       - master
   pull_request:
 
+env:
+  RUST_VERSION: 1.75.0
+
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
 
+      - run: rustup override set ${{ env.RUST_VERSION }}
       - uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
 
       - run: cargo run