Updated to actions/cache@v4.

.github/workflows/build.yml

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 3722a05..50e3203 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -29,7 +29,7 @@
         id: llvm-revision
         run: |
           echo "revision=$(git -C ${{ github.workspace }}/llvm-project rev-parse HEAD)" >> "$GITHUB_OUTPUT"
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         id: llvm-build
         with:
           path: ${{ github.workspace }}/build/llvm-project
@@ -78,7 +78,7 @@
         id: llvm-revision
         run: |
           echo "revision=$(git -C ${{ github.workspace }}/llvm-project rev-parse HEAD)" >> "$GITHUB_OUTPUT"
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         id: llvm-build
         with:
           path: ${{ github.workspace }}/build/llvm-project
@@ -126,7 +126,7 @@
         id: llvm-revision
         run: |
           echo "revision=$(git -C ${{ github.workspace }}/llvm-project rev-parse HEAD)" >> "$GITHUB_OUTPUT"
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         id: llvm-build
         with:
           path: ${{ github.workspace }}/build/llvm-project