Allow rgbasm and rgblink to use stdout and stdin as input and output

src/link/main.c

@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 
@@ -126,7 +127,14 @@ FILE *openFile(char const *fileName, char const *mode)
 	if (!fileName)
 		return NULL;
 
-	FILE *file = fopen(fileName, mode);
+	FILE *file;
+	if (strcmp(fileName, "-") != 0) {
+		file = fopen(fileName, mode);
+	} else if (strchr(mode, 'r')) {
+		file = fdopen(0, mode);
+	} else {
+		file = fdopen(1, mode);
+	}
 
 	if (!file)
 		err(1, "Could not open file \"%s\"", fileName);