[clang] Make libBasic not depend on MC

Reduces numbers of files built for clang-format from 575 to 449.

Requires two small changes:

1. Don't use llvm::ExceptionHandling in LangOptions. This isn't
   even quite the right type since we don't use all of its values.
   Tweaks the changes made in:
   - https://reviews.llvm.org/D93215
   - https://reviews.llvm.org/D93216

2. Move section name validation code added (long ago) in commit 30ba67439 out
   of libBasic into Sema and base the check on the triple. This is a bit less
   OOP-y, but completely in line with what we do in many other places in Sema.

No behavior change.

Differential Revision: https://reviews.llvm.org/D101463

utils/gn/secondary/clang/lib/Basic/BUILD.gn

@@ -49,7 +49,6 @@ static_library("Basic") {
     "//clang/include/clang/Sema:AttrParsedAttrKinds",
     "//clang/include/clang/Sema:AttrSpellingListIndex",
     "//llvm/include/llvm/Config:llvm-config",
-    "//llvm/lib/MC",
     "//llvm/lib/Support",
   ]
   include_dirs = [ "." ]

utils/gn/secondary/clang/lib/Sema/BUILD.gn

@@ -25,6 +25,7 @@ static_library("Sema") {
     "//clang/lib/Edit",
     "//clang/lib/Lex",
     "//llvm/lib/Frontend/OpenMP",
+    "//llvm/lib/MC",
     "//llvm/lib/Support",
   ]
   sources = [

utils/gn/secondary/clang/tools/clang-format/BUILD.gn

@@ -12,6 +12,7 @@ executable("clang-format") {
     "//clang/lib/Frontend/",
     "//clang/lib/Sema/",
     "//llvm/lib/IR",
+    "//llvm/lib/MC",
   ]
   sources = [ "ClangFormat.cpp" ]
 }