[cmake] Prevent building with BUILD_SHARED_LIBS and LLVM_LINK_LLVM_DYLIB

Summary: This doesn't work, so error early if someone tries it. Reviewers: beanz, smeenai, compnerd, phosek Reviewed By: beanz Subscribers: mgorny, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D70160

Author: tstellar

llvm/CMakeLists.txt

@@ -584,6 +584,10 @@ else()
  option(LLVM_BUILD_LLVM_DYLIB "Build libllvm dynamic library"${LLVM_BUILD_LLVM_DYLIB_default})
 endif()
 
+if (LLVM_LINK_LLVM_DYLIB ANDBUILD_SHARED_LIBS)
+ message(FATAL_ERROR "Cannot enable BUILD_SHARED_LIBS with LLVM_LINK_LLVM_DYLIB. We recommend disabling BUILD_SHARED_LIBS.")
+endif()
+
 option(LLVM_OPTIMIZED_TABLEGEN "Force TableGen to be built with optimization"OFF)
 if(CMAKE_CROSSCOMPILINGOR (LLVM_OPTIMIZED_TABLEGEN AND (LLVM_ENABLE_ASSERTIONS ORCMAKE_CONFIGURATION_TYPES)))
  set(LLVM_USE_HOST_TOOLS ON)