[SourceKit] Ignore LLVM arguments in 'compile' request

LLVM arguments processing is a process global state. At this point,
there's no way to localize it to a CompilerInstance. For now, ignore any
LLVM arguemnts, so options from another compilation doesn't affect other
compilations.

rdar://86809003

Author: rintaro

lib/IDE/CompileInstance.cpp

@@ -263,6 +263,11 @@ bool CompileInstance::setupCI(
     return false;
   }
 
+  // Since LLVM arguments are parsed into a global state, LLVM can't handle
+  // multiple argument sets in a process simultaneously. So let's ignore them.
+  // FIXME: Remove this if possible.
+  invocation.getFrontendOptions().LLVMArgs.clear();
+
   /// Declare the frontend to be used for multiple compilations.
   invocation.getFrontendOptions().ReuseFrontendForMutipleCompilations = true;
 

test/SourceKit/Compile/basic.swift

@@ -1,5 +1,3 @@
-// REQUIRES: rdar86809003
-
 // RUN: %empty-directory(%t)
 // RUN: %empty-directory(%t/out)
 // RUN: split-file %s %t