fix(linux): correct PS escape for $GIT_CLONE_URL in UseGitClone clone cmd

In PS double-quoted strings, backslash does NOT escape '$'.
Only backtick does ('`$'). The previous '\' was being
expanded as a PS variable (undefined), triggering StrictMode error:
'Cannot retrieve variable \ because it has not been set.'

Replace '\$' with '`$' so the literal shell variable reference
\ is emitted correctly to the SSH command.

scripts/Invoke-RemoteBuild.ps1

@@ -225,7 +225,7 @@ if ($GuestOS -eq 'Linux') {
             # PAT injected via env var inside SSH session — never in args
             $envCloneCmd = "export GIT_CLONE_URL='$cloneTargetUrl'; git clone --depth 1 --branch '$CloneBranch'"
             if ($CloneSubmodules) { $envCloneCmd += ' --recurse-submodules' }
-            $envCloneCmd += " `"`\$GIT_CLONE_URL`" '$GuestLinuxWorkDir'; unset GIT_CLONE_URL"
+            $envCloneCmd += " `"`$GIT_CLONE_URL`" '$GuestLinuxWorkDir'; unset GIT_CLONE_URL"
             Invoke-SshCommand -IP $IPAddress -User $SshUser -KeyPath $SshKeyPath -Command $envCloneCmd
         } else {
             Invoke-SshCommand -IP $IPAddress -User $SshUser -KeyPath $SshKeyPath -Command $cloneCmd