delete unused function in ClangExpressionParser`

[ldrumm]

Summary

[git 65dafa83] introduced the GetBuiltinIncludePath function copied from cfe/lib/Driver/CC1Options.cpp

This function is no longer used in lldb's expression parser and I believe it is safe to remove it.

lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

 using namespace clang;
 using namespace llvm;
 using namespace lldb_private;
 
 //===----------------------------------------------------------------------===//
 // Utility Methods for Clang
 //===----------------------------------------------------------------------===//
 
-std::string GetBuiltinIncludePath(const char *Argv0) {
-    SmallString<128> P(llvm::sys::fs::getMainExecutable(
-        Argv0, (void *)(intptr_t) GetBuiltinIncludePath));
-
-    if (!P.empty()) {
-        llvm::sys::path::remove_filename(P); // Remove /clang from foo/bin/clang
-        llvm::sys::path::remove_filename(P); // Remove /bin   from foo/bin
-
-        // Get foo/lib/clang/<version>/include
-        llvm::sys::path::append(P, "lib", "clang", CLANG_VERSION_STRING,
-                                "include");
-    }
-
-    return P.str();
-}
 
 class ClangExpressionParser::LLDBPreprocessorCallbacks : public PPCallbacks
 {
     ClangModulesDeclVendor     &m_decl_vendor;
     ClangPersistentVariables   &m_persistent_vars;
     StreamString                m_error_stream;
     bool                        m_has_errors = false;