[flang] Fix cmake errors when building the Decimal and runtime libraries standalone

[jpenix-quic]

Summary

Currently, cmake gives errors that check_cxx_compiler_flag and append are
unknown when building the Decimal and runtime libraries standalone. Add
the appropriate include resolve this.

[jeanPerier]

flang/runtime/CMakeLists.txt

43

Isn't include(HandleLLVMOptions) enough given CheckCXXCompilerFlag seems to be already included by HandleLLVMOptions at [1] ?

[1]: https://github.com/llvm/llvm-project/blob/8d3ab9dfc4d49062e045d6d5db419975b81da7e4/llvm/cmake/modules/HandleLLVMOptions.cmake#L13

[jpenix-quic]

Remove unnecessary include(CheckCXXCompilerFlag)s

[jpenix-quic]

flang/runtime/CMakeLists.txt

43

Oops, yep, HandleLLVMOptions is enough. Thanks for catching this!

[jeanPerier]

Thanks, LGTM.

flang/lib/Decimal/CMakeLists.txt

list(INSERT CMAKE_MODULE_PATH 0
     "${LLVM_COMMON_CMAKE_UTILS}"
     "${LLVM_COMMON_CMAKE_UTILS}/Modules"
     "${LLVM_CMAKE_UTILS}"
     "${LLVM_CMAKE_UTILS}/modules"
     )
 
   include(AddLLVM)
   include(AddFlang)
+  include(HandleLLVMOptions)
 
   include(TestBigEndian)
   test_big_endian(IS_BIGENDIAN)
   if (IS_BIGENDIAN)
     add_compile_definitions(FLANG_BIG_ENDIAN=1)
   else ()
     add_compile_definitions(FLANG_LITTLE_ENDIAN=1)
   endif ()

flang/runtime/CMakeLists.txt

list(INSERT CMAKE_MODULE_PATH 0
     "${LLVM_COMMON_CMAKE_UTILS}"
     "${LLVM_COMMON_CMAKE_UTILS}/Modules"
     "${LLVM_CMAKE_UTILS}"
     "${LLVM_CMAKE_UTILS}/modules"
     )
 
   include(AddLLVM)
   include(AddFlang)
+  include(HandleLLVMOptions)
 
   include(TestBigEndian)
   test_big_endian(IS_BIGENDIAN)
   if (IS_BIGENDIAN)
     add_compile_definitions(FLANG_BIG_ENDIAN=1)
   else ()
     add_compile_definitions(FLANG_LITTLE_ENDIAN=1)
   endif ()
   include_directories(BEFORE