enable symbolizer on any platform with backtrace(3)

Summary:
Now that symbolizer has precise feature flags, enable
FOLLY_USE_SYMBOLIZER on any platform that has backtrace(3), which is
all that's needed to get a useful stack trace printed in the signal
handler.

Reviewed By: yfeldblum, luciang

Differential Revision: D23361609

fbshipit-source-id: b124f7fd01e94f90d8f8586555a64bd6e412040c

CMake/folly-deps.cmake

@@ -165,7 +165,7 @@ find_package(Backtrace)
 
 set(FOLLY_HAVE_BACKTRACE ${Backtrace_FOUND})
 set(FOLLY_HAVE_DWARF ${LIBDWARF_FOUND})
-if (APPLE OR (FOLLY_HAVE_ELF AND FOLLY_HAVE_DWARF AND FOLLY_HAVE_BACKTRACE AND LIBUNWIND_FOUND))
+if (NOT WIN32)
   set(FOLLY_USE_SYMBOLIZER ON)
 endif()
 message(STATUS "Setting FOLLY_USE_SYMBOLIZER: ${FOLLY_USE_SYMBOLIZER}")