[libc++abi] Remove the LIBCXXABI_ENABLE_PIC option

Instead, people should be using CMAKE_POSITION_INDEPENDENT_CODE to control
whether they want to use PIC or not. We should try to avoid reinventing
the wheel whenever CMake natively supports something.

This makes libc++abi consistent with libc++ and libunwind.

Differential Revision: https://reviews.llvm.org/D103973

libcxx/cmake/caches/Apple.cmake

@@ -15,6 +15,5 @@ set(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS ON CACHE BOOL "")
 set(LIBCXX_HERMETIC_STATIC_LIBRARY ON CACHE BOOL "")
 set(LIBCXXABI_HERMETIC_STATIC_LIBRARY ON CACHE BOOL "")
 
-set(LIBCXXABI_ENABLE_PIC OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_ASSERTIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_FORGIVING_DYNAMIC_CAST ON CACHE BOOL "")

libcxx/docs/ReleaseNotes.rst

@@ -65,3 +65,7 @@ API Changes
   While this is technically both an API and an ABI break, we do not expect
   ``std::pointer_safety`` to have been used at all in real code, since we
   never implemented the underlying support for garbage collection.
+
+- The `LIBCXXABI_ENABLE_PIC` CMake option was removed. If you are building your
+  own libc++abi from source and were using `LIBCXXABI_ENABLE_PIC`, please use
+  `CMAKE_POSITION_INDEPENDENT_CODE=ON` instead.

libcxxabi/CMakeLists.txt

@@ -82,7 +82,6 @@ option(LIBCXXABI_ENABLE_EXCEPTIONS
   When disabled, libc++abi does not support stack unwinding and other exceptions-related features." ON)
 option(LIBCXXABI_ENABLE_ASSERTIONS "Enable assertions independent of build mode." ON)
 option(LIBCXXABI_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
-option(LIBCXXABI_ENABLE_PIC "Build Position-Independent Code, even in static library" ON)
 option(LIBCXXABI_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." OFF)
 option(LIBCXXABI_ENABLE_STATIC_UNWINDER "Statically link the LLVM unwinder." OFF)

libcxxabi/src/CMakeLists.txt

@@ -201,10 +201,6 @@ if (LIBCXXABI_ENABLE_SHARED)
                           DEFINE_SYMBOL
                             "")
 
-  if(LIBCXXABI_ENABLE_PIC)
-    set_target_properties(cxxabi_shared PROPERTIES POSITION_INDEPENDENT_CODE ON)
-  endif()
-
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_shared")
   if (LIBCXXABI_INSTALL_SHARED_LIBRARY)
     list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_shared")
@@ -262,10 +258,6 @@ if (LIBCXXABI_ENABLE_STATIC)
                           OUTPUT_NAME
                             "c++abi")
 
-  if(LIBCXXABI_ENABLE_PIC)
-    set_target_properties(cxxabi_static PROPERTIES POSITION_INDEPENDENT_CODE ON)
-  endif()
-
   if(LIBCXXABI_HERMETIC_STATIC_LIBRARY)
     append_flags_if_supported(CXXABI_STATIC_LIBRARY_FLAGS -fvisibility=hidden)
     # If the hermetic library doesn't define the operator new/delete functions