[ClangImporter] Don't pass API notes options when compiling bitcode. (#10425)

Avoids a bogus "argument unused" warning, since bitcode compilation
doesn't bother to set up much of a Clang AST context. (-embed-bitcode
compiles in two steps: source -> bitcode, then bitcode -> object
file. This is about the second step.)

Patch by Bob Wilson, who's currently on vacation but wanted this to
get in sooner rather than later.

rdar://problem/31372950

Author: jrose-apple

lib/ClangImporter/ClangImporter.cpp

@@ -620,6 +620,23 @@ getNormalInvocationArguments(std::vector<std::string> &invocationArgStrs,
       "-Xclang", "-fmodule-format=obj",
     });
   }
+
+  // Enable API notes alongside headers/in frameworks.
+  invocationArgStrs.push_back("-fapinotes-modules");
+
+  // Add API notes paths.
+  for (const auto &searchPath : searchPathOpts.ImportSearchPaths) {
+    invocationArgStrs.push_back("-iapinotes-modules");
+    invocationArgStrs.push_back(searchPath);
+  }
+  invocationArgStrs.push_back("-iapinotes-modules");
+  invocationArgStrs.push_back(searchPathOpts.RuntimeLibraryImportPath);
+
+  // Map the Swift major version into the API notes version for Swift. This
+  // has the effect of allowing API notes to effect changes only on Swift
+  // major versions, not minor versions.
+  invocationArgStrs.push_back("-fapinotes-swift-version=" +
+                              llvm::itostr(languageVersion[0]));
 }
 
 static void
@@ -691,23 +708,6 @@ addCommonInvocationArguments(std::vector<std::string> &invocationArgStrs,
   for (auto extraArg : importerOpts.ExtraArgs) {
     invocationArgStrs.push_back(extraArg);
   }
-
-  // Enable API notes alongside headers/in frameworks.
-  invocationArgStrs.push_back("-fapinotes-modules");
-
-  // Add API notes paths.
-  for (const auto &searchPath : searchPathOpts.ImportSearchPaths) {
-    invocationArgStrs.push_back("-iapinotes-modules");
-    invocationArgStrs.push_back(searchPath);
-  }
-  invocationArgStrs.push_back("-iapinotes-modules");
-  invocationArgStrs.push_back(searchPathOpts.RuntimeLibraryImportPath);
-
-  // Map the Swift major version into the API notes version for Swift. This
-  // has the effect of allowing API notes to effect changes only on Swift
-  // major versions, not minor versions.
-  invocationArgStrs.push_back("-fapinotes-swift-version=" +
-    llvm::itostr(ctx.LangOpts.EffectiveLanguageVersion[0]));
 }
 
 bool ClangImporter::canReadPCH(StringRef PCHFilename) {

test/Frontend/embed-bitcode.ll

@@ -23,6 +23,7 @@ target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 ; CHECK-IMPORTER: clang
 ; CHECK-IMPORTER: -fembed-bitcode
 ; CHECK-IMPORTER: -target
+; CHECK-IMPORTER-NOT: argument unused
 
 define i32 @f0() nounwind ssp {
        ret i32 0