tests: OOT build fixes etc.

tests/Makefile: fix out-of-tree build issues

Also:

- win64: align(16) MEM_DEBUG user memory
  on win64 the struct jmp_buf in the TCCState structure which we
  allocate by tcc_malloc needs alignment 16 because the msvcrt
  setjmp uses MMX instructions.

- libtcc_test.c: win32/64 need __attribute__((dllimport)) for
  extern data objects

- tcctest.c: exclude stuff that gcc does not compile
  except for relocation_test() the other issues are mostly ASM
  related.  We should probably check GCC versions but I have
  no idea which mingw/gcc versions support what and which don't.

- lib/Makefile: use tcc to compile libtcc1.a (except on arm
  which needs arm-asm

tests/libtcc_test.c

@@ -15,11 +15,15 @@ int add(int a, int b)
     return a + b;
 }
 
+/* this strinc is referenced by the generated code */
 const char hello[] = "Hello World!";
 
 char my_program[] =
 "#include <tcclib.h>\n" /* include the "Simple libc header for TCC" */
 "extern int add(int a, int b);\n"
+"#ifdef _WIN32\n" /* dynamically linked data needs 'dllimport' */
+" __attribute__((dllimport))\n"
+"#endif\n"
 "extern const char hello[];\n"
 "int fib(int n)\n"
 "{\n"