don't fail if directory exists

Author: Enchufa2

.github/workflows/ci.yaml

@@ -64,7 +64,7 @@ jobs:
         run: ${{matrix.r }} CMD build --no-build-vignettes --no-manual .
 
       - name: Set flags
-        run: mkdir ~/.R && echo "CXXFLAGS += ${{ matrix.cxxflags }}" > ~/.R/Makevars
+        run: mkdir -p ~/.R && echo "CXXFLAGS += ${{ matrix.cxxflags }}" > ~/.R/Makevars
 
       - name: Check
         run: CI=true ${{ matrix.r }} CMD check --no-vignettes --no-manual Rcpp_*.tar.gz