Use mold for coverage

.circleci/config.yml

@@ -1,7 +1,7 @@
 version: 2.1
 
 orbs:
-  codecov: codecov/codecov@3.2.5
+  codecov: codecov/codecov@4.1.0
   win: circleci/windows@5.0
 
 commands:
@@ -1089,13 +1089,18 @@ jobs:
 
   coverage:
     docker:
-      - image: rust:1.74.0
+      - image: rust:1.78.0-alpine3.19
     environment:
       # Limit the number of parallel jobs to avoid OOM crashes during doc testing
       RUST_TEST_THREADS: 8
     resource_class: medium+
     steps:
       - checkout
+      - run:
+          name: Install necessary packages
+          command: |
+            apk update
+            apk add mold clang curl coreutils gnupg
       - run:
           name: Install grcov
           command: |
@@ -1114,8 +1119,11 @@ jobs:
             grcov . -s packages/std --binary-path ./target/debug -t lcov -o ./reports/std.info
             grcov . -s packages/vm --binary-path ./target/debug -t lcov -o ./reports/vm.info
           environment:
-            RUSTFLAGS: "-Cinstrument-coverage"
+            RUSTFLAGS: "-Clinker=clang -Clink-arg=-fuse-ld=/usr/bin/mold -Cinstrument-coverage"
             LLVM_PROFILE_FILE: "cosmwasm-%p-%m.profraw"
+      - run:
+          name: Quick fix for GPG error in Codecov
+          command: mkdir -p ~/.gnupg
       - codecov/upload:
           file: reports/core.info
           flags: cosmwasm-core