Fix git safe.directory path normalization in DockerBuild.ps1

The regex '\\' was looking for double backslashes but Windows paths
have single backslashes. Changed to '\' to properly convert C:\path
to C:/path for git safe.directory config.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gfraiteur

DockerBuild.ps1

@@ -1136,7 +1136,7 @@ $( ($GitDirectories | ForEach-Object { "    '$_'" }) -join ",`n" )
 foreach (`$dir in `$gitDirectories) {
     if (`$dir) {
         # Normalize path: convert backslashes to forward slashes, add trailing slash
-        `$normalizedDir = (`$dir -replace '\\\\', '/').TrimEnd('/') + '/'
+        `$normalizedDir = (`$dir -replace '\\', '/').TrimEnd('/') + '/'
         git config --global --add safe.directory `$normalizedDir
     }
 }

src/PostSharp.Engineering.BuildTools/Resources/DockerBuild.ps1

@@ -1136,7 +1136,7 @@ $( ($GitDirectories | ForEach-Object { "    '$_'" }) -join ",`n" )
 foreach (`$dir in `$gitDirectories) {
     if (`$dir) {
         # Normalize path: convert backslashes to forward slashes, add trailing slash
-        `$normalizedDir = (`$dir -replace '\\\\', '/').TrimEnd('/') + '/'
+        `$normalizedDir = (`$dir -replace '\\', '/').TrimEnd('/') + '/'
         git config --global --add safe.directory `$normalizedDir
     }
 }