Improve an error message.

Before:
$ ld.lld --plugin-opt=Os
ld.lld: error: --plugin-opt: number expected, but got 's'

After:
$ ld.lld --plugin-opt=Os
ld.lld: error: --plugin-opt=Os: number expected, but got 's'

llvm-svn: 322315

Author: rui314

lld/ELF/Driver.cpp

@@ -584,7 +584,8 @@ static bool getCompressDebugSections(opt::InputArgList &Args) {
 static int parseInt(StringRef S, opt::Arg *Arg) {
   int V = 0;
   if (!to_integer(S, V, 10))
-    error(Arg->getSpelling() + ": number expected, but got '" + S + "'");
+    error(Arg->getSpelling() + "=" + Arg->getValue() +
+          ": number expected, but got '" + S + "'");
   return V;
 }
 

lld/test/ELF/lto/opt-level.ll

@@ -19,7 +19,7 @@
 ; RUN:   FileCheck --check-prefix=INVALID1 %s
 ; RUN: not ld.lld -o %t3 -m elf_x86_64 -e main --plugin-opt=Ofoo %t.o 2>&1 | \
 ; RUN:   FileCheck --check-prefix=INVALID2 %s
-; INVALID2: --plugin-opt: number expected, but got 'foo'
+; INVALID2: --plugin-opt=Ofoo: number expected, but got 'foo'
 
 ; RUN: not ld.lld -o %t3 -m elf_x86_64 -e main --lto-O-1 %t.o 2>&1 | \
 ; RUN:   FileCheck --check-prefix=INVALIDNEGATIVE1 %s