[lldb] Remove default llvm::Triple argument from ClangASTContext constructor

Creating an ASTContext with an unknown triple is rarely a good idea (as usually
all our ASTs have a valid triple that is either from the host or the target) and the
default argument makes it far to easy to implicitly create such an AST. Let's
remove it and force people to pass a triple.

The only place where we don't pass a triple is a DWARFASTParserClangTests
where we now just pass the host triple instead (the test doesn't depend on any
triple so this shouldn't change anything).

Author: Teemperor

lldb/include/lldb/Symbol/ClangASTContext.h

@@ -61,7 +61,7 @@ class ClangASTContext : public TypeSystem {
   ///               certain characteristics of the ASTContext and its types
   ///               (e.g., whether certain primitive types exist or what their
   ///               signedness is).
-  explicit ClangASTContext(llvm::Triple triple = llvm::Triple());
+  explicit ClangASTContext(llvm::Triple triple);
 
   /// Constructs a ClangASTContext that uses an existing ASTContext internally.
   /// Useful when having an existing ASTContext created by Clang.

lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp

@@ -9,14 +9,15 @@
 #include "Plugins/SymbolFile/DWARF/DWARFASTParserClang.h"
 #include "Plugins/SymbolFile/DWARF/DWARFDIE.h"
 #include "TestingSupport/SubsystemRAII.h"
+#include "lldb/Host/HostInfo.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
 class DWARFASTParserClangTests : public testing::Test {
-  SubsystemRAII<FileSystem, ClangASTContext> subsystems;
+  SubsystemRAII<FileSystem, HostInfo, ClangASTContext> subsystems;
 };
 
 namespace {
@@ -38,7 +39,7 @@ class DWARFASTParserClangStub : public DWARFASTParserClang {
 // defining here, causing this test to fail, feel free to delete it.
 TEST_F(DWARFASTParserClangTests,
        EnsureAllDIEsInDeclContextHaveBeenParsedParsesOnlyMatchingEntries) {
-  ClangASTContext ast_ctx;
+  ClangASTContext ast_ctx(HostInfoBase::GetTargetTriple());
   DWARFASTParserClangStub ast_parser(ast_ctx);
 
   DWARFUnit *unit = nullptr;