[clang] [Clang][Hexagon] Use --cstdlib flag to choose Picolibc (PR #183257)

[Alexey Karyakin via cfe-commits]

================
@@ -745,29 +767,33 @@ void HexagonToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   }
 }
 
-void HexagonToolChain::addLibCxxIncludePaths(
-    const llvm::opt::ArgList &DriverArgs,
-    llvm::opt::ArgStringList &CC1Args) const {
-  SmallString<128> Dir;
-  getBaseIncludeDir(Dir);
-  llvm::sys::path::append(Dir, "c++", "v1");
-  addLibStdCXXIncludePaths(Dir, "", "", DriverArgs, CC1Args);
-}
+void HexagonToolChain::AddClangCXXStdlibIncludeArgs(
+    const ArgList &DriverArgs, ArgStringList &CC1Args) const {
+  if (DriverArgs.hasArg(options::OPT_nostdinc, options::OPT_nostdlibinc,
+                        options::OPT_nostdincxx))
+    return;
 
-void HexagonToolChain::addLibStdCxxIncludePaths(
-    const llvm::opt::ArgList &DriverArgs,
-    llvm::opt::ArgStringList &CC1Args) const {
   SmallString<128> Dir;
-  getBaseIncludeDir(Dir);
-  llvm::sys::path::append(Dir, "c++");
-  addLibStdCXXIncludePaths(Dir, "", "", DriverArgs, CC1Args);
+  getBaseIncludeDir(DriverArgs, Dir);
+
+  CXXStdlibType Type = GetCXXStdlibType(DriverArgs);
+  switch (Type) {
+  case ToolChain::CST_Libcxx:
+    llvm::sys::path::append(Dir, "c++", "v1");
+    addSystemInclude(DriverArgs, CC1Args, Dir);
+    break;
+  case ToolChain::CST_Libstdcxx:
+    llvm::sys::path::append(Dir, "c++");
+    addSystemInclude(DriverArgs, CC1Args, Dir);
+    break;
+  }
----------------
quic-akaryaki wrote:

It seems addLibStdCXXIncludePaths() is the standard way to add C++ include path and other targets use it. I think it's better to stick to it unless there is a good reason. Is the failing test the only reason?

https://github.com/llvm/llvm-project/pull/183257