Revert "[Modules] Prevent #import to reenter header if not building a module."

This reverts commit r310605. Richard pointed out a better way to achieve
this, which I'll post a patch for soon.

llvm-svn: 310775

clang/lib/Lex/HeaderSearch.cpp

@@ -1143,7 +1143,7 @@ bool HeaderSearch::ShouldEnterIncludeFile(Preprocessor &PP,
     // headers find in the wild might rely only on #import and do not contain
     // controlling macros, be conservative and only try to enter textual headers
     // if such macro is present.
-    if (FileInfo.isCompilingModuleHeader && !FileInfo.isModuleHeader &&
+    if (!FileInfo.isModuleHeader &&
         FileInfo.getControllingMacro(ExternalLookup))
       TryEnterHdr = true;
     return TryEnterHdr;

clang/test/Modules/Inputs/import-textual/x.h

@@ -1,6 +0,0 @@
-#ifndef RANDOM_DEP
-
-@interface X
-@end
-
-#endif // RANDOM_DEP

clang/test/Modules/import-textual-nomodules.m

@@ -1,8 +0,0 @@
-// RUN: rm -rf %t
-// RUN: %clang_cc1 -fsyntax-only -fmodules -fimplicit-module-maps -I%S/Inputs/import-textual -fmodules-cache-path=%t %s -verify
-
-// expected-no-diagnostics
-
-#import "x.h"
-#import "x.h"
-