add linux support to runtime build

runtime/include/isa/ppc_isa_config.h

@@ -11,11 +11,22 @@ inline constexpr bool MkwStateFreeAbiEnabled(uint32_t) noexcept
     return true;
 }
 
+#if defined(_WIN32)
 #define MKW_PPC_FORCE_INLINE __forceinline
 #define MKW_PPC_NO_INLINE __declspec(noinline)
+#define MKW_PPC_INTERNAL_CALL __regcall
+#else
+// __forceinline/__declspec are MS-extension keywords Clang only recognizes when targeting
+// Windows (MSVC or mingw); native Linux Clang needs the GNU-attribute spellings instead.
+// __regcall has no portable non-Windows equivalent worth chasing here - the extra register
+// args it saves matter for the hot PPC interpreter loop on Windows, but plain calls are fine
+// elsewhere.
+#define MKW_PPC_FORCE_INLINE __attribute__((always_inline)) inline
+#define MKW_PPC_NO_INLINE __attribute__((noinline))
+#define MKW_PPC_INTERNAL_CALL
+#endif
 #define MKW_PPC_ALWAYS_INLINE_BODY __attribute__((always_inline))
 #define MKW_PPC_COLD __attribute__((cold))
-#define MKW_PPC_INTERNAL_CALL __regcall
 
 
 using MkwStateFreeResult2 = uint64_t __attribute__((ext_vector_type(2)));