Fix Linux VST compilation

cmake/modules/CheckCXXPreprocessor.cmake

@@ -0,0 +1,33 @@
+
+macro(CHECK_CXX_PREPROCESSOR VAR DIRECTIVE)
+	string(RANDOM DEFINED_KEY)
+	string(RANDOM UNDEFINED_KEY)
+
+	set(TMP_FILENAME "${CMAKE_CURRENT_BINARY_DIR}/CxxTmp/src.cpp")
+	SET(SRC "
+		#if ${DIRECTIVE}
+		#error ${DEFINED_KEY}
+		#else
+		#error ${UNDEFINED_KEY}
+		#endif
+		")
+	file(WRITE ${TMP_FILENAME} "${SRC}")
+	try_compile(RESULT_VAR
+		${CMAKE_CURRENT_BINARY_DIR}
+		${TMP_FILENAME}
+		OUTPUT_VARIABLE OUTPUT_VAR
+	)
+
+	if(OUTPUT_VAR MATCHES ${DEFINED_KEY})
+		set(${VAR} ON)
+	elseif(OUTPUT_VAR MATCHES ${UNDEFINED_KEY})
+		set(${VAR} OFF)
+	else()
+		message(FATAL_ERROR "Can't determine if \"${DIRECTIVE}\" is true.")
+	endif()
+endmacro()
+
+
+macro(CHECK_CXX_DEFINE VAR DEFINE)
+	CHECK_CXX_PREPROCESSOR(${VAR} "defined(${DEFINE})")
+endmacro()