Fix garbage characters at EOF causing an infinite loop

src/asm/lexer.cpp

@@ -1636,6 +1636,10 @@ static Token yylex_SKIP_TO_ENDC(); // Forward declaration for `yylex_NORMAL`
 
 // Must stay in sync with the `switch` in `yylex_NORMAL`!
 static bool isGarbageCharacter(int c) {
+	// EOF is not garbage (it can't be reported anyway)
+	if (c == EOF) {
+		return false;
+	}
 	// Whitespace characters are not garbage, even the non-"printable" ones
 	if (isWhitespace(c)) {
 		return false;
@@ -1645,7 +1649,7 @@ static bool isGarbageCharacter(int c) {
 		return true;
 	}
 	// All other printable characters are not garbage (i.e. `yylex_NORMAL` handles them), and
-	// all other nonprintable characters are garbage (including '\0' and EOF)
+	// all other nonprintable characters are garbage (including '\0')
 	return !isPrintable(c);
 }
 

test/asm/garbage-before-eof.asm

@@ -0,0 +1 @@
+MACRO<EFBFBD>

test/asm/garbage-before-eof.err

@@ -0,0 +1,5 @@
+error: Invalid character 0xEB (is the file UTF-8?)
+    at garbage-before-eof.asm(1)
+error: syntax error, unexpected end of buffer, expecting ? or symbol
+    at garbage-before-eof.asm(1)
+Assembly aborted with 2 errors!