[Driver] Suggest valid integrated tools

[modocache]

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

[bkramer]

The -cc1 stuff isn't exactly user-facing, so we didn't put so much emphasis on providing great error messages there. This change LGTM.

[modocache]

Great, thanks for the review @bkramer!

test/Driver/unknown-arg.c

 // RUN: not %clang %s -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -### 2>&1 | \
 // RUN: FileCheck %s
 // RUN: not %clang %s -stdlibs=foo -hell -version -### 2>&1 | \
 // RUN: FileCheck %s --check-prefix=DID-YOU-MEAN
 // RUN: %clang_cl -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -### -c -- %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CL
 // RUN: %clang_cl -Brepo -### -- %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CL-DID-YOU-MEAN
 // RUN: not %clang_cl -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -c -Werror=unknown-argument -### -- %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CL-ERROR
 // RUN: not %clang_cl -helo -Werror=unknown-argument -### -- %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CL-ERROR-DID-YOU-MEAN
 // RUN: %clang_cl -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -c -Wno-unknown-argument -### -- %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=SILENT
+// 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'
 // CHECK: error: unknown argument: '-%d'
 // CHECK: error: unknown argument: '-HHHH'
 // CHECK: error: unknown argument: '-munknown-to-clang-option'
 // CHECK: error: unknown argument: '-print-stats'
 // CHECK: error: unknown argument: '-funknown-to-clang-option'

 // CL-ERROR: error: unknown argument ignored in clang-cl: '-%d'
 // CL-ERROR: error: unknown argument ignored in clang-cl: '-HHHH'
 // CL-ERROR: error: unknown argument ignored in clang-cl: '-munknown-to-clang-option'
 // CL-ERROR: error: unknown argument ignored in clang-cl: '-print-stats'
 // CL-ERROR: error: unknown argument ignored in clang-cl: '-funknown-to-clang-option'
 // CL-ERROR-DID-YOU-MEAN: error: unknown argument ignored in clang-cl '-helo' (did you mean '-help'?)
 // SILENT-NOT: error:
 // SILENT-NOT: warning:
+// 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
 
 // IGNORED: warning: unknown warning option '-Wunknown-to-clang-option'

tools/driver/driver.cpp

 static int ExecuteCC1Tool(ArrayRef<const char *> argv, StringRef Tool) {
   void *GetExecutablePathVP = (void *)(intptr_t) GetExecutablePath;
   if (Tool == "")
     return cc1_main(argv.slice(2), argv[0], GetExecutablePathVP);
   if (Tool == "as")
     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;
 }
 
 int main(int argc_, const char **argv_) {
   llvm::sys::PrintStackTraceOnErrorSignal(argv_[0]);
   llvm::PrettyStackTraceProgram X(argc_, argv_);
   llvm::llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.