Makefile: Fix regression in .SILENT rule

Since commit d74e651b78 (Makefiles: Re-implement makefile target path
escaping and quoting, 2020-04-10, v3.18.0-rc1~334^2~1), `WriteMakeRule`
now correctly escapes `$` in make target paths as `$$`.  However, this
caused an existing call site to escape the `$(VERBOSE)` variable
reference in the `.SILENT` prefix, making it ineffective.  Sub-makefiles
are invoked with `MAKESILENT`, so this bug matters only for the `all`
target, which emits progress messages from toplevel.

Before:

    # Suppress display of executed commands.
    $$(VERBOSE).SILENT:

After:

    # Suppress display of executed commands.
    $(VERBOSE).SILENT:

1 files changed, 4 insertions, 3 deletions

diff --git a/Source/cmLocalUnixMakefileGenerator3.cxx b/Source/cmLocalUnixMakefileGenerator3.cxx
index 4545a8e..de1461a 100644
--- a/Source/cmLocalUnixMakefileGenerator3.cxx
+++ b/Source/cmLocalUnixMakefileGenerator3.cxx
@@ -713,9 +713,10 @@ void cmLocalUnixMakefileGenerator3::WriteSpecialTargetsTop(
     // "VERBOSE=1" to be added as a make variable which will change the
     // name of this special target.  This gives a make-time choice to
     // the user.
-    this->WriteMakeRule(makefileStream,
-                        "Suppress display of executed commands.",
-                        "$(VERBOSE).SILENT", no_depends, no_commands, false);
+    // Write directly to the stream since WriteMakeRule escapes '$'.
+    makefileStream << "#Suppress display of executed commands.\n"
+                      "$(VERBOSE).SILENT:\n"
+                      "\n";
   }
 
   // Work-around for makes that drop rules that have no dependencies