Enable thread_local code more broadly.

This was only being enabled on Windows, Linux, and FreeBSD. (FreeBSD
only had it enabled in the legacy build system, not in cmake.)

`thread_local` is part of C++11, so now that we require C++17
or later and more recent compilers, this should work everywhere
that threading does, so only disable it within a `SINGLE_THREAD`
build.

CMakeLists.txt

@@ -188,9 +188,6 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
   message(STATUS "Platform: Linux")
   list(APPEND Z3_COMPONENT_CXX_DEFINES "-D_LINUX_")
-  if (TARGET_ARCHITECTURE STREQUAL "x86_64")
-    list(APPEND Z3_COMPONENT_CXX_DEFINES "-D_USE_THREAD_LOCAL")
-  endif()
 elseif (CMAKE_SYSTEM_NAME STREQUAL "Android")
   message(STATUS "Platform: Android")
   list(APPEND Z3_COMPONENT_CXX_DEFINES "-D_ANDROID_")

scripts/mk_util.py

@@ -2640,8 +2640,6 @@ def mk_config():
         if is64():
             if not sysname.startswith('CYGWIN') and not sysname.startswith('MSYS') and not sysname.startswith('MINGW'):
                 CXXFLAGS     = '%s -fPIC' % CXXFLAGS
-            if sysname == 'Linux' or sysname == 'FreeBSD':
-                CPPFLAGS = '%s -D_USE_THREAD_LOCAL' % CPPFLAGS
         elif not LINUX_X64:
             CXXFLAGS     = '%s -m32' % CXXFLAGS
             LDFLAGS      = '%s -m32' % LDFLAGS

src/util/memory_manager.cpp

@@ -215,7 +215,7 @@ void * memory::allocate(char const* file, int line, char const* obj, size_t s) {
 }
 #endif
 
-#if !defined(SINGLE_THREAD) && (defined(_WINDOWS) || defined(_USE_THREAD_LOCAL))
+#if !defined(SINGLE_THREAD)
 // ==================================
 // ==================================
 // THREAD LOCAL VERSION