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/tcctest.c

@@ -2667,6 +2667,9 @@ int reltab[3] = { 1, 2, 3 };
 int reltab[3] = { 1, 2, 3 };
 
 int *rel1 = &reltab[1];
+int *rel2 = &reltab[2];
+
+#ifdef _WIN64
 void relocation_test(void) {}
 #else
 void getmyaddress(void)
@@ -2695,6 +2698,7 @@ void relocation_test(void)
     fptr();
 #ifdef __LP64__
     printf("pa_symbol=0x%lx\n", __pa_symbol() >> 63);
+#endif
 }
 #endif
 
@@ -3127,8 +3131,10 @@ void other_constraints_test(void)
 
 void other_constraints_test(void)
 {
+    unsigned long ret;
     int var;
 #ifndef _WIN64
+    __asm__ volatile ("mov %P1,%0" : "=r" (ret) : "p" (&var));
     printf ("oc1: %d\n", ret == (unsigned long)&var);
 #endif
 }
@@ -3203,9 +3209,11 @@ void test_high_clobbers(void)
        registers if they are clobbered and if it's the high 8 x86-64
        registers.  This is fragile for GCC as the constraints do not
        correctly capture the data flow, but good enough for us.  */
+    asm volatile("mov $0x4542, %%r12" : "=r" (val):: "memory");
     clobber_r12();
 #ifndef _WIN64
     asm volatile("mov %%r12, %0" : "=r" (val2) : "r" (val): "memory");
+    printf("asmhc: 0x%x\n", val2);
 #endif
 #endif
 }