Support b2_targets input also for Windows

Author: Flamefire

.github/workflows/reusable.yml

@@ -616,7 +616,11 @@ jobs:
           # Use Bash which is more flexible than CMD and we can reuse the logic
           . ci/enforce.sh
           echo "B2_FULL_ARGS=${B2_ARGS[@]}" >> "$GITHUB_ENV"
-          echo "B2_TOOLSET=$B2_TOOLSET" >> "$GITHUB_ENV"
+          echo "SELF=$SELF" >> "$GITHUB_ENV"
+          if [[-z "$B2_TARGETS" ]]; then
+            B2_TARGETS=libs/$SELF/test
+          fi
+          echo "B2_TARGETS=$B2_TARGETS" >> "$GITHUB_ENV"
         env:
           B2_TOOLSET: ${{matrix.toolset}}
           B2_TARGET_OS: ${{matrix.target-os}}
@@ -626,6 +630,7 @@ jobs:
           B2_LINK: ${{inputs.b2_link}}
           B2_VARIANT: ${{inputs.b2_variant}}
           SELF: ${{inputs.library_folder}}
+          B2_TARGETS: ${{inputs.b2_targets}}
 
       - name: Run tests
         if: '!matrix.coverage'