[cmake] Remove line of code that is setting LLVM_BINARY_DIR to CMAKE_BINARY_DIR (i.e., SWIFT_BINARY_DIR).

This bug was in tree before I began to make my changes. I uncovered the bug when
I was thinking about whether or not this line of code was dead and thus looked
at how it was used.

rdar://26154980

Author: gottesmm

cmake/modules/SwiftSharedCMakeConfig.cmake

@@ -230,7 +230,6 @@ macro(swift_common_standalone_build_config product is_cross_compiling)
 
   set(LLVM_MAIN_INCLUDE_DIR "${LLVM_MAIN_SRC_DIR}/include")
   set(CLANG_MAIN_INCLUDE_DIR "${CLANG_MAIN_SRC_DIR}/include")
-  set(LLVM_BINARY_DIR ${CMAKE_BINARY_DIR})
   set(CMARK_MAIN_INCLUDE_DIR "${CMARK_MAIN_SRC_DIR}/src")
   set(CMARK_BUILD_INCLUDE_DIR "${PATH_TO_CMARK_BUILD}/src")