try appending to CMAKE_PREFIX_PATH instead?

Author: lgray

.github/workflows/ci.yml

@@ -179,7 +179,7 @@ jobs:
             GMP_LIB_DIR='C:\vcpkg\packages\gmp_x64-windows\lib'
             MPFR_INC_DIR='C:\vcpkg\packages\mpfr_x64-windows\include'
             MPFR_LIB_DIR='C:\vcpkg\packages\mpfr_x64-windows\lib'
-            CMAKE_PREFIX_PATH="C:\vcpkg\packages\getopt-win32_x64-windows\share\unofficial-getopt-win32;$CMAKE_PREFIX_PATH"
+            CMAKE_PREFIX_PATH+=';C:\vcpkg\packages\getopt-win32_x64-windows\share\unofficial-getopt-win32'
 
 
       - name: Upload wheels