Set policy CMP0177 and follow the documented recommendations regarding DESTINATION paths.

CMakeLists.txt

@@ -14,6 +14,11 @@ endif()
 if (POLICY CMP0167)
   cmake_policy(SET CMP0167 OLD)
 endif()
+# CMake 3.31+ Use normalization rules on install DESTINATION
+# command. We shouldn't be impacted so allow the new behavior.
+if (POLICY CMP0177)
+  cmake_policy(SET CMP0177 NEW)
+endif()
 
 project (gnucash
     VERSION 5.12

common/cmake_modules/GncAddSchemeTargets.cmake

@@ -309,8 +309,8 @@ function(gnc_add_scheme_targets _TARGET)
   if(SCHEME_TGT_TEST)
     add_dependencies(check ${_TARGET})
   else()
-    install(FILES ${_TARGET_FILES} DESTINATION ${CMAKE_INSTALL_PREFIX}/${GUILE_REL_SITECCACHEDIR}/${SCHEME_TGT_OUTPUT_DIR})
-    install(FILES ${SCHEME_TGT_SOURCES} DESTINATION ${CMAKE_INSTALL_PREFIX}/${GUILE_REL_SITEDIR}/${SCHEME_TGT_OUTPUT_DIR})
+    install(FILES ${_TARGET_FILES} DESTINATION ${GUILE_REL_SITECCACHEDIR}/${SCHEME_TGT_OUTPUT_DIR})
+    install(FILES ${SCHEME_TGT_SOURCES} DESTINATION ${GUILE_REL_SITEDIR}/${SCHEME_TGT_OUTPUT_DIR})
   endif()
 endfunction()
 

common/cmake_modules/GncAddTest.cmake

@@ -26,6 +26,7 @@ function(get_guile_env)
     list(APPEND env "PATH=${fpath}")
     set(compiled_path "${CMAKE_BINARY_DIR}/${GUILE_REL_SITECCACHEDIR}")
     string(REGEX REPLACE "^([A-Za-z]):" "/\\1" compiled_path ${compiled_path})
+    string(REGEX REPLACE "\\\\" "/" compiled_path ${compiled_path})
     list(APPEND env GUILE_LOAD_COMPILED_PATH=${compiled_path})
   endif()
   list(APPEND env "GNC_MODULE_PATH=${_GNC_MODULE_PATH}")
@@ -54,19 +55,21 @@ function(get_guile_env)
   if (MINGW64)
     set(new_path "")
     foreach(load_item ${guile_load_path})
-      string(REGEX REPLACE "^([A-Za-z]):" "/\\1" load_item ${load_item})
+#      string(REGEX REPLACE "^([A-Za-z]):" "/\\1" load_item ${load_item})
+      string(REGEX REPLACE "\\\\" "/" load_item ${load_item})
       list(APPEND new_path ${load_item})
     endforeach(load_item)
     set(guile_load_path ${new_path})
 
     set(new_path "")
     foreach(load_item ${guile_load_compiled_path})
-      string(REGEX REPLACE "^([A-Za-z]):" "/\\1" load_item ${load_item})
+#      string(REGEX REPLACE "^([A-Za-z]):" "/\\1" load_item ${load_item})
+      string(REGEX REPLACE "\\\\" "/" load_item ${load_item})
       list(APPEND new_path ${load_item})
     endforeach(load_item)
     set(guile_load_compiled_path ${new_path})
   endif()
-  if (WIN32 AND NOT MINGW64)
+  if (WIN32)
       string(REPLACE ";" "\\\\;" GUILE_LOAD_PATH "${guile_load_path}")
       string(REPLACE ";" "\\\\;" GUILE_LOAD_COMPILED_PATH "${guile_load_compiled_path}")
   else()

libgnucash/backend/dbi/test/CMakeLists.txt

@@ -34,7 +34,6 @@ set(test_dbi_backend_HEADERS test-dbi-business-stuff.h test-dbi-stuff.h)
 
 set_dist_list(test_dbi_backend_DIST ${test_dbi_backend_SOURCES} ${test_dbi_backend_HEADERS} test-dbi.xml CMakeLists.txt )
 
-# This test does not work on Win32
 if (WITH_SQL)
   gnc_add_test(test-backend-dbi "${test_dbi_backend_SOURCES}"
     BACKEND_DBI_TEST_INCLUDE_DIRS BACKEND_DBI_TEST_LIBS