Strip preceeding -Xclang when stripping -fcolor-diagnostics or -fdiagnostics-color

Summary: Fixes clangd/clangd#279. We were removing the color options but not the preceeding -Xclang which causes errors since the -Xclang would now apply to the next option in the list of options. Now, when removing a color option, we check if there was a preceeding -Xclang and remove it as well.

Patch By @DaanDeMeyer !

Reviewers: sammccall, kadircet

Reviewed By: sammccall

Subscribers: ilya-biryukov, usaxena95

Differential Revision: https://reviews.llvm.org/D75019

(cherry picked from commit da236f2)

Author: kadircet

clang/lib/Tooling/ArgumentsAdjusters.cpp

@@ -42,6 +42,12 @@ ArgumentsAdjuster getClangSyntaxOnlyAdjuster() {
       if (!Arg.startswith("-fcolor-diagnostics") &&
           !Arg.startswith("-fdiagnostics-color"))
         AdjustedArgs.push_back(Args[i]);
+      // If we strip a color option, make sure we strip any preceeding `-Xclang`
+      // option as well.
+      // FIXME: This should be added to most argument adjusters!
+      else if (!AdjustedArgs.empty() && AdjustedArgs.back() == "-Xclang")
+        AdjustedArgs.pop_back();
+
       if (Arg == "-fsyntax-only")
         HasSyntaxOnly = true;
     }