ci:windows: "$HOME" needed

Author: scivision

.github/workflows/ci_windows.yml

@@ -4,8 +4,6 @@ env:
   CTEST_NO_TESTS_ACTION: error
   CTEST_PARALLEL_LEVEL: 0
   CMAKE_BUILD_PARALLEL_LEVEL: 4
-  CMAKE_INSTALL_PREFIX: ~/libs
-  CMAKE_PREFIX_PATH: ~/libs
 
 on:
   push:
@@ -27,6 +25,11 @@ jobs:
     timeout-minutes: 30
     runs-on: windows-latest
 
+    # Windows needs these defined within the job for $HOME
+    env:
+      CMAKE_INSTALL_PREFIX: $HOME/libs
+      CMAKE_PREFIX_PATH: $HOME/libs
+
     steps:
     - uses: msys2/setup-msys2@v2
       with: