[flang] Fix CMake bug in the definition of flang-new

[awarzynski]

Summary

Recent patch that improved Flang's compatibility with respect to how LLVM
dynamic libraries should be linked (and specified in CMake recipes),
introduced a bug in the definition of flang-new:

• https://reviews.llvm.org/D87893

More specifically, add_flang_tool does not support the
LINK_COMPONENTS CMake argument. Instead, one should set
LLVM_LINK_COMPONENTS before calling add_flang_tool.

This patch reverts the change for flang-new from
https://reviews.llvm.org/D87893, and instead:

• sets LLVM_LINK_COMPONENTS
• calls clang_target_link_libraries to add Clang dependencies

[awarzynski]

Revert accidental and unnecessary change

[DavidTruby]

LGTM

[serge-sans-paille]

Thanks for fixing the bug so quickly!

flang/CMakeLists.txt

if(CMAKE_COMPILER_IS_GNUCXX)
     set(USE_NO_MAYBE_UNINITIALIZED 1)
   endif()
 
   include(CMakeParseArguments)
   include(AddLLVM)
   include(HandleLLVMOptions)
   include(VersionFromVCS)
 
+  if(FLANG_BUILD_NEW_DRIVER)
+    include(AddClang)
+  endif()
+
   if(LINK_WITH_FIR)
     include(TableGen)
     find_package(MLIR REQUIRED CONFIG)
     # Use SYSTEM for the same reasons as for LLVM includes
     include_directories(SYSTEM ${MLIR_INCLUDE_DIRS})
     # If the user specifies a relative path to MLIR_DIR, the calls to include
     # MLIR modules fail. Append the absolute path to MLIR_DIR instead.
     get_filename_component(MLIR_DIR_ABSOLUTE ${MLIR_DIR} REALPATH)

flang/tools/flang-driver/CMakeLists.txt

 # Infrastructure to build flang driver entry point. Flang driver depends on
 # LLVM libraries.
 
 # Set your project compile flags.
 link_directories(${LLVM_LIBRARY_DIR})
 
+set( LLVM_LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  Option
+  Support
+)
+
 add_flang_tool(flang-new
   driver.cpp
   fc1_main.cpp
-
-  LINK_COMPONENTS
-
-  ${LLVM_COMMON_COMPONENTS}
-  Support
-  Target
-  Option
 )
 
-# Link against LLVM and Clang libraries
 target_link_libraries(flang-new
   PRIVATE
   flangFrontend
   flangFrontendTool
+)
+
+clang_target_link_libraries(flang-new
+  PRIVATE
   clangDriver
   clangBasic
   clangFrontend
 )
-
-install(TARGETS flang-new DESTINATION bin)