[Darwin] Use errorHandler from liblldCommon

Summary:
Error handling in liblldCore and the Darwin toolchain prints to an
output stream. A TODO in the project explained that a diagnostics
interface resembling Clang's should be added.

For now, the simple diagnostics interface defined in liblldCommon seems
like an improvement. It prints colors when they're available, uses locks
for thread-safety, and abstracts away the `"error: "` and newline
literal strings that litter the Darwin toolchain code.

To use the liblldCommon error handler, a link dependency is added to
the liblldDriver library.

Test Plan:
1. check-lld
2. Invoke `ld64.lld -r` in a terminal that supports color output.
   Confirm that "ld64.lld: error: -arch not specified and could not be inferred"
   is output, and that the "error:" is colored red!

Reviewers: ruiu, smeenai

Reviewed By: ruiu

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D47998

1 files changed, 2 insertions, 5 deletions

diff --git a/lld/unittests/DriverTests/DarwinLdDriverTest.cpp b/lld/unittests/DriverTests/DarwinLdDriverTest.cpp
index 0c1d779ce4c..e2e634a4cb2 100644
--- a/lld/unittests/DriverTests/DarwinLdDriverTest.cpp
+++ b/lld/unittests/DriverTests/DarwinLdDriverTest.cpp
@@ -23,8 +23,7 @@ using namespace lld;
 
 namespace lld {
 namespace mach_o {
-bool parse(llvm::ArrayRef<const char *> args, MachOLinkingContext &ctx,
-           raw_ostream &diagnostics);
+bool parse(llvm::ArrayRef<const char *> args, MachOLinkingContext &ctx);
 }
 }
 
@@ -42,9 +41,7 @@ protected:
 
   bool parse(std::vector<const char *> args) {
     args.insert(args.begin(), "ld");
-    std::string errorMessage;
-    raw_string_ostream os(errorMessage);
-    return mach_o::parse(args, _ctx, os);
+    return mach_o::parse(args, _ctx);
   }
 
   MachOLinkingContext _ctx;