[ELF] - Linkerscript: Add `~` as separate math token.

Previously we did not support following:
foo = ~0xFF;
and had to add space before numeric value:
foo = ~ 0xFF

That was constistent with ld.bfd < 2.30, which shows:
script.txt:3: undefined symbol `~2' referenced in expression,
but inconsistent with gold.

It was fixed for ld.bfd 2.30 as well:
https://sourceware.org/bugzilla/show_bug.cgi?id=22267

Differential revision: https://reviews.llvm.org/D36508

llvm-svn: 315569

lld/ELF/ScriptLexer.cpp

@@ -164,7 +164,7 @@ bool ScriptLexer::atEOF() { return ErrorCount || Tokens.size() == Pos; }
 // Split a given string as an expression.
 // This function returns "3", "*" and "5" for "3*5" for example.
 static std::vector<StringRef> tokenizeExpr(StringRef S) {
-  StringRef Ops = "+-*/:!"; // List of operators
+  StringRef Ops = "+-*/:!~"; // List of operators
 
   // Quoted strings are literal strings, so we don't want to split it.
   if (S.startswith("\""))