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