Fix regression on reconfigure with unnormalized -DCMAKE_<LANG>_COMPILER=

Since commit 3f2a5971c0 (Modules: CMAKE_*_COMPILER convert path to cmake
path, 2023-12-02, v3.29.0-rc1~292^2) we normalize the path to the
compiler.  Update our logic that checks whether the compiler has changed
to account for path normalization.

Fixes: #25883
Issue: #25456

Source/cmGlobalGenerator.cxx

@@ -28,6 +28,7 @@
 #include "cm_codecvt_Encoding.hxx"
 
 #include "cmAlgorithms.h"
+#include "cmCMakePath.h"
 #include "cmCPackPropertiesGenerator.h"
 #include "cmComputeTargetDepends.h"
 #include "cmCryptoHash.h"
@@ -270,17 +271,14 @@ void cmGlobalGenerator::ResolveLanguageCompiler(const std::string& lang,
 
   std::string changeVars;
   if (cname && !optional) {
-    std::string cnameString;
+    cmCMakePath cachedPath;
     if (!cmSystemTools::FileIsFullPath(*cname)) {
-      cnameString = cmSystemTools::FindProgram(*cname);
+      cachedPath = cmSystemTools::FindProgram(*cname);
     } else {
-      cnameString = *cname;
+      cachedPath = *cname;
     }
-    std::string pathString = path;
-    // get rid of potentially multiple slashes:
-    cmSystemTools::ConvertToUnixSlashes(cnameString);
-    cmSystemTools::ConvertToUnixSlashes(pathString);
-    if (cnameString != pathString) {
+    cmCMakePath foundPath = path;
+    if (foundPath.Normal() != cachedPath.Normal()) {
       cmValue cvars = this->GetCMakeInstance()->GetState()->GetGlobalProperty(
         "__CMAKE_DELETE_CACHE_CHANGE_VARS_");
       if (cvars) {

Tests/RunCMake/CompilerChange/CompilerPath-stdout.txt

@@ -0,0 +1,2 @@
+-- CMAKE_C_COMPILER is '[^']*/Tests/RunCMake/CompilerChange/cc1.sh'
+-- CACHE_ENTRY='cached'

Tests/RunCMake/CompilerChange/CompilerPath.cmake

@@ -0,0 +1,3 @@
+enable_language(C)
+message(STATUS "CMAKE_C_COMPILER is '${CMAKE_C_COMPILER}'")
+message(STATUS "CACHE_ENTRY='${CACHE_ENTRY}'")

Tests/RunCMake/CompilerChange/RunCMakeTest.cmake

@@ -35,3 +35,13 @@ block()
   set(ENV{RunCMake_TEST} "EmptyCompiler")
   run_cmake_with_options(EmptyCompiler -DCMAKE_C_COMPILER=)
 endblock()
+
+block()
+  set(cc1_dot ${RunCMake_BINARY_DIR}/./cc1.sh)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/CompilerPath-build)
+  set(RunCMake_TEST_VARIANT_DESCRIPTION "-step1")
+  run_cmake_with_options(CompilerPath "-DCMAKE_C_COMPILER=${cc1_dot}" -DCACHE_ENTRY=cached)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  set(RunCMake_TEST_VARIANT_DESCRIPTION "-step2")
+  run_cmake_with_options(CompilerPath "-DCMAKE_C_COMPILER=${cc1_dot}")
+endblock()