[PDB] memicmp only exists on Windows, use StringRef::compare_lower instead

llvm-svn: 336469
diff --git a/llvm/lib/DebugInfo/PDB/Native/GSIStreamBuilder.cpp b/llvm/lib/DebugInfo/PDB/Native/GSIStreamBuilder.cpp
index c8437d2..2f0f76b 100644
--- a/llvm/lib/DebugInfo/PDB/Native/GSIStreamBuilder.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/GSIStreamBuilder.cpp
@@ -98,8 +98,8 @@
   if (LLVM_UNLIKELY(!isAsciiString(S1) || !isAsciiString(S2)))
     return memcmp(S1.data(), S2.data(), LS) < 0;
 
-  // Both strings are ascii, use memicmp.
-  return memicmp(S1.data(), S2.data(), LS) < 0;
+  // Both strings are ascii, perform a case-insenstive comparison.
+  return S1.compare_lower(S2.data()) < 0;
 }
 
 void GSIHashStreamBuilder::finalizeBuckets(uint32_t RecordZeroOffset) {