[llvm-cov] Warn when -arch spec is missing/invalid for universal binary (reland)

llvm-cov reports a poor error message when the -arch specifier is
missing or invalid, and a binary has multiple slices. Make the error
message more specific.

(This version of the patch avoids using llvm::none_of -- the way I used
the utility caused compile errors on many bots, possibly because the
wrong overload of `none_of` was selected.)

rdar://40312677

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
index ec840a3..87dab21 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -816,6 +816,8 @@ static std::string getCoverageMapErrString(coveragemap_error Err) {
     return "Malformed coverage data";
   case coveragemap_error::decompression_failed:
     return "Failed to decompress coverage data (zlib)";
+  case coveragemap_error::invalid_or_missing_arch_specifier:
+    return "`-arch` specifier is invalid or missing for universal binary";
   }
   llvm_unreachable("A value of coveragemap_error has no message.");
 }