Make -frewrite-includes handle -include correctly

The `-include "file"` option implicitly adds a leading #include
to the main source; however, there's no explicit #include, which
left -frewrite-includes emitting an unmatched #endif at the end
of the included text.

This corrects a bug in 4a16b51.

clang/lib/Frontend/Rewrite/InclusionRewriter.cpp

@@ -444,8 +444,11 @@ void InclusionRewriter::Process(FileID FileId,
               if (Mod)
                 OS << "#pragma clang module end /*"
                    << Mod->getFullModuleName(true) << "*/\n";
-              OS << "#endif /* " << getIncludedFileName(Inc)
-                 << " expanded by -frewrite-includes */" << LocalEOL;
+              // There's no #include, therefore no #if, for -include files.
+              if (FromFile != PredefinesBuffer) {
+                OS << "#endif /* " << getIncludedFileName(Inc)
+                   << " expanded by -frewrite-includes */" << LocalEOL;
+              }
 
               // Add line marker to indicate we're returning from an included
               // file.

clang/test/Frontend/rewrite-includes-cli-include.c

@@ -3,7 +3,6 @@ main_file_line
 // CHECK: {{^}}# 1 "<built-in>"{{$}}
 // CHECK-NEXT: {{^}}# 1 "{{.*[/\\]Inputs(/|\\\\)}}rewrite-includes2.h" 1{{$}}
 // CHECK-NEXT: {{^}}int included_line2;{{$}}
-// CHECK-NEXT: {{^}}#endif /* rewrite-includes2.h expanded by -frewrite-includes */{{$}}
 // CHECK-NEXT: {{^}}# 1 "<built-in>" 2{{$}}
 // CHECK-NEXT: {{^}}# 1 "{{.*}}rewrite-includes-cli-include.c"{{$}}
 // CHECK-NEXT: FileCheck