[workflows] Update path to Flang build directory

The following Flang commit has changed the default location of the Flang build
directory, resulting in CI failures in the classic-flang-llvm-project:

flang-compiler/flang@054bde3

This patch updates the path name in the CI workflows.

Author: bryanpkc

.github/workflows/flang-arm64-tests.yml

@@ -62,9 +62,9 @@ jobs:
       - name: Copy llvm-lit
         run: |
           cd ${{ env.build_path }}/flang
-          cp ${{ env.build_path }}/classic-flang-llvm-project/build/bin/llvm-lit build/bin/.
+          cp ${{ env.build_path }}/classic-flang-llvm-project/build/bin/llvm-lit build/flang/bin/
 
       - name: Test flang
         run: |
-          cd ${{ env.build_path }}/flang/build
+          cd ${{ env.build_path }}/flang/build/flang
           make check-all

.github/workflows/flang-tests.yml

@@ -73,9 +73,9 @@ jobs:
       - name: Copy llvm-lit
         run: |
           cd ../../flang
-          cp ../classic-flang-llvm-project/classic-flang-llvm-project/build/bin/llvm-lit build/bin/.
+          cp ../classic-flang-llvm-project/classic-flang-llvm-project/build/bin/llvm-lit build/flang/bin/
 
       - name: Test flang
         run: |
-          cd ../../flang/build
+          cd ../../flang/build/flang
           make check-all