Move entire mingw64 folder

mv the whole mingw64 folder instead of moving things piecemeal.

An investigation of how the windows image installs mingw64 (https://github.com/actions/runner-images/blob/main/images/windows/scripts/build/Install-Mingw64.ps1) shows that it just extracts the whole thing to /c/mingw64, so it should be safe and complete to mv the whole folder.

.github/actions/test-fc/action.yml

@@ -52,7 +52,8 @@ runs:
         set -x
 
         # Move the old libgfortran-5.dll back to its original place.
-        mv "$RUNNER_TEMP/mingw64/libgfortran-5.dll" /c/mingw64/bin/libgfortran-5.dll 
+        mkdir -p /c/mingw64/bin/
+        [ -f "$RUNNER_TEMP/mingw64/bin/libgfortran-5.dll"   ] && mv "$RUNNER_TEMP/mingw64/bin/libgfortran-5.dll" /c/mingw64/bin/libgfortran-5.dll
         # Confirm that we find the gcc12 one ahead of the gcc11 one.
         which -a libgfortran-5.dll
         

setup-fortran.sh

@@ -87,11 +87,7 @@ install_gcc_choco()
     echo "GCC $version already installed"
   else
     # otherwise hide preinstalled mingw compilers
-    mkdir "$RUNNER_TEMP/mingw64"
-    mv /c/mingw64/bin/gfortran "$RUNNER_TEMP/mingw64/gfortran"
-    mv /c/mingw64/bin/libgfortran-5.dll "$RUNNER_TEMP/mingw64/libgfortran-5.dll"
-    mv /c/mingw64/bin/gcc "$RUNNER_TEMP/mingw64/gcc"
-    mv /c/mingw64/bin/g++ "$RUNNER_TEMP/mingw64/g++"
+    mv /c/mingw64 "$RUNNER_TEMP/"
     # ...and install selected version
     case $version in
       13)