[mach-o] fix uninitialized variable

llvm-svn: 194290
diff --git a/lld/lib/ReaderWriter/MachO/MachOLinkingContext.cpp b/lld/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
index 005c8f7..4f5a9be 100644
--- a/lld/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
@@ -115,6 +115,7 @@
     : _outputFileType(MH_EXECUTE), _outputFileTypeStatic(false),
       _doNothing(false), _arch(arch_unknown), _os(OS::macOSX), _osMinVersion(0),
       _pageZeroSize(unspecifiedPageZeroSize), 
+      _pageSize(4096), 
       _compatibilityVersion(0), _currentVersion(0),
       _deadStrippableDylib(false), _kindHandler(nullptr) {}