[Driver] Suggest valid integrated tools

Summary:
There are only two valid integrated Clang driver tools: `-cc1` and
`-cc1as`. If a user asks for an unknown tool, such as `-cc1asphalt`,
an error message is displayed to indicate that there is no such tool,
but the message doesn't indicate what the valid options are.

Include the valid options in the error message.

Test Plan: `check-clang`

Reviewers: sepavloff, bkramer, phosek

Reviewed By: bkramer

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D42004

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322517 91177308-0d34-0410-b5e6-96231b3b80d8

Author: modocache

test/Driver/unknown-arg.c

@@ -14,6 +14,8 @@
 // RUN: FileCheck %s --check-prefix=SILENT
 // RUN: not %clang -cc1as -hell --version -debug-info-macros 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CC1AS-DID-YOU-MEAN
+// RUN: not %clang -cc1asphalt -help 2>&1 | \
+// RUN: FileCheck %s --check-prefix=UNKNOWN-INTEGRATED
 
 // CHECK: error: unknown argument: '-cake-is-lie'
 // CHECK: error: unknown argument: '-%0'
@@ -46,7 +48,7 @@
 // CC1AS-DID-YOU-MEAN: error: unknown argument '-hell', did you mean '-help'?
 // CC1AS-DID-YOU-MEAN: error: unknown argument '--version', did you mean '-version'?
 // CC1AS-DID-YOU-MEAN: error: unknown argument '-debug-info-macros', did you mean '-debug-info-macro'?
-
+// UNKNOWN-INTEGRATED: error: unknown integrated tool 'asphalt'. Valid tools include '-cc1' and '-cc1as'.
 
 // RUN: %clang -S %s -o %t.s  -Wunknown-to-clang-option 2>&1 | FileCheck --check-prefix=IGNORED %s
 

tools/driver/driver.cpp

@@ -311,7 +311,8 @@ static int ExecuteCC1Tool(ArrayRef<const char *> argv, StringRef Tool) {
     return cc1as_main(argv.slice(2), argv[0], GetExecutablePathVP);
 
   // Reject unknown tools.
-  llvm::errs() << "error: unknown integrated tool '" << Tool << "'\n";
+  llvm::errs() << "error: unknown integrated tool '" << Tool << "'. "
+               << "Valid tools include '-cc1' and '-cc1as'.\n";
   return 1;
 }