[MSVC] workaround mvn macro and detect ARM64 (#407)

Fixed MSVC AArch64 build

* Detect AArch64 target properly when compiling by MSVC
* Workaround the issue caused by MSVC defining a mvn macro

---------

Co-authored-by: Petr Kobalicek <kobalicek.petr@gmail.com>

src/asmjit/arm/a64emitter.h

@@ -11,6 +11,14 @@
 #include "../arm/a64instdb.h"
 #include "../arm/a64operand.h"
 
+// MSVC targeting AArch64 defines a lot of macros without underscores clashing
+// with AArch64 instruction names. We have to workaround until it's fixed in SDK.
+#if defined(_MSC_VER) && defined(mvn)
+  #define ASMJIT_RESTORE_MSVC_AARCH64_MACROS
+  #pragma push_macro("mvn")
+  #undef mvn
+#endif
+
 ASMJIT_BEGIN_SUB_NAMESPACE(a64)
 
 #define ASMJIT_INST_0x(NAME, ID) \
@@ -1225,4 +1233,9 @@ class Emitter : public BaseEmitter, public EmitterExplicitT<Emitter> {
 
 ASMJIT_END_SUB_NAMESPACE
 
+// Restore undefined MSVC AArch64 macros.
+#if defined(ASMJIT_RESTORE_MSVC_AARCH64_MACROS)
+  #pragma pop_macro("mvn")
+#endif
+
 #endif // ASMJIT_ARM_A64EMITTER_H_INCLUDED

src/asmjit/core/api-config.h

@@ -172,7 +172,7 @@ namespace asmjit {
   #define ASMJIT_ARCH_X86 0
 #endif
 
-#if defined(__arm64__) || defined(__aarch64__)
+#if defined(_M_ARM64) || defined(__arm64__) || defined(__aarch64__)
 # define ASMJIT_ARCH_ARM 64
 #elif defined(_M_ARM) || defined(_M_ARMT) || defined(__arm__) || defined(__thumb__) || defined(__thumb2__)
   #define ASMJIT_ARCH_ARM 32